Why are paper Christmas cards still a thing? Millennials, for once, are to thank.

Party invitations that once came to mailboxes now arrive via email or Facebook, and calendar apps are stiff competition for physical datebooks. Smartphones give us more ways to keep in touch than ever.

But old-fashioned paper greeting cards, delivered via snail mail, remain a holiday staple.

Some consumers are opting out of an annual ritual they say is time-consuming and redundant when we share photos and status updates daily on social media. But for others, the idea of taking the time to exchange tangible tokens of holiday cheer is more appealing than ever at a time when buzzing and pinging digital devices never seem to cease demanding our attention. That’s true even if finding the perfect card now involves sitting at a laptop, editing digital photos and clicking through dozens of template designs.

Sales of greeting cards have been fairly stable in the U.S. over the past five or six years, with consumers buying around 6.5 billion greeting cards and 1.6 billion holiday cards per year, said Peter Doherty, executive director of the Greeting Card Association. Those figures don’t include custom photo cards, the kind many families order from places like Shutterfly or Walgreens.

But that stability is an improvement after several years of declining sales, Doherty said.

“People were starting to use email as a replacement, but over time they found they weren’t making the same meaningful connection,” he said.

Not everyone has returned to paper. Susan Wojcik, 43, of Chicago’s Lincoln Park neighborhood, estimates she only receives about a 10th of the cards she used to, though she doesn’t particularly miss them and stopped sending them herself about five years ago.

“I keep in touch so many other ways,” Wojcik said.

But those who continue to send holiday greetings on paper tend to be particularly drawn to the idea of a physical object with a personal sentiment, according to makers and sellers of greeting cards.

Carolina Ojeda, 27, of Little Village, who was shopping for cards for close family and friends Tuesday at Paper Source in the Lincoln Park area, said she enjoys picking out cards and wouldn’t want to break the tradition by going digital.

“I’m very old-school,” said Ojeda, who looks forward to receiving holiday cards in the mail too.

“That’s the cheer of Christmas,” she said.

Even a wave of enthusiasm for e-cards a few years ago subsided as consumers found them “too fleeting,” said Patrick Priore, chief merchant at Chicago-based Paper Source.

The biggest fans of e-cards tend to be people who also send lots of paper cards and want one more way to keep in touch, said Lindsey Roy, chief marketing officer at Hallmark Greetings. The company still offers them but doesn’t see them driving growth, she said.

Lydia Fields, 31, of Lincoln Park, said she’s starting to receive more holiday cards as her friends have started having kids but few, if any, arrive by email.

“I think we all like a good old-fashioned card,” Fields said.

That doesn’t mean consumers are buying the same cards they always have. Greeting card publishers are trying to innovate with cards consumers can customize or fancier cards that don’t feel generic, said Marisa Lifschutz, an analyst at industry research firm IBISWorld. Those items tend to be more profitable for card-makers, though they don’t appear to be leading to growth in the overall industry, which also includes makers of products like calendars and postcards that are facing similar digital competition, she said.

Fields, for instance, used online design service Minted to create a card featuring her 13-month-old daughter, Lottie. The photo and handwritten notes she added felt personal, but pre-printing envelopes saved time, she said.

Custom photo cards appear to be gaining popularity, said Doherty, of the Greeting Card Association, though his organization doesn’t track those sales. Shutterfly, which sells custom cards through its namesake and Tinyprints brands, doesn’t disclose figures for individual business segments like custom cards. But the company said half the revenue from its consumer businesses comes in the fourth quarter.

The personalized cards have been “a consistent business,” said Mickey Mericle, chief marketing officer at Shutterfly, who declined to comment further on sales. During the busiest days between Thanksgiving and Christmas, the company prints more than 8 million cards per day.

Designing a card can be more time-consuming than picking a box off a shelf. Shutterfly tries to balance giving customers creative control with features that save time, like using artificial intelligence to recommend promising photos or automatically crop them, Mericle said. Online design service Minted, meanwhile, has stylists who can send users five suggested card designs if they text a photo and answer a couple of questions about their preferred greeting and aesthetic.

Deerfield-based Walgreens, meanwhile, added new design options over the past two years. It used to print only on photo paper but now offers cardstock and some designs embossed with foil and a choice of square or rounded edges.

Even when people start with a digital photo and design their cards online, they’re still choosing to create something that will end up on paper, Paper Source’s Priore said.

“There’s something very tactile and emotionally connective,” Priore said. “People save cards. It’s a keepsake, but it’s also an expression of whatever sentiment you’re trying to convey.”

Custom printed cards are the fastest-growing slice of the holiday cards business at Paper Source, though sales of individual and box-set holiday cards also have been growing, he said.

Millennials now account for the largest share of greeting card buyers, and they prefer cards that make a personal statement, Doherty said.

They seem particularly drawn to the idea of customizing a card, Shutterfly’s Mericle said. They “don’t want a canned saying from a box of cards” to represent them, she said. “Millennials want to make it their own.”

Mericle said millennials are comfortable with more informal designs and photos and don’t feel obligated to wait for traditional milestones like starting a family to send holiday cards. Pet-focused cards have been popular, she said.

But a desire for cards that feel personal doesn’t always mean designing something from scratch.

Consumers who take the trouble to pick out a card at a store still want it to feel like it was chosen specifically for the recipient, said Shayna Norwood, owner of Steel Petal Press.

Norwood designs and sells greeting cards at her store in Logan Square and through other retailers, including Paper Source.

“It’s a reaction to the digital world we live in,” she said. “People take it really far the other way and want a card that says exactly what they think.”

Norwood thinks that trend could benefit smaller publishers that aren’t necessarily trying to design cards for the broadest possible audience. Steel Petal Press’ designs tend to be snarky and sassy, and many top-sellers feature curse words, Norwood said.

She knows that’s not for everyone and stocks some cards by other designers, but they still have to fit her audience. A line of particularly sentimental cards didn’t do well, said Norwood, who said she aims to offer items that are “funny or beautiful or both.”

But even the biggest name in the greeting card business says it’s working on designing cards that don’t feel generic.

Hallmark sees growth coming from higher-end cards like its Signature line, designed to feel like keepsakes, with embellishments like beads, ribbons or charm necklaces, and a new line of “mantle-worthy” pop-up cards introduced this holiday season, Roy said.

The pop-up cards, called Paper Wonder, are exceeding expectations, and Hallmark plans to release them for other holidays, including Valentine’s Day, she said.

In addition to focusing on specialty cards, Hallmark also has updated some messages for younger buyers, Roy said. There are cards that don’t assume everyone has a traditional family structure and some with messages alluding to spending the holidays apart, since more young adults live far from family.

The goal, she said, is a card that “feels like it was written totally for me and my relationship” – even if it was plucked from a chain store’s shelf.

Roy thinks the lasting appeal of paper cards comes from being “an antidote to too much digital.”

When a card arrives in the mail, it shows someone put time and effort into choosing the design and sending it, said Cindy Magder, 46, of Lincoln Park, who sends friends and relatives custom-printed cards with a family photo each year.

“It’s not a gift, but it feels like it is,” Magder said. “I feel like I’m special if someone thought to send it.”