A reader whom I'll call "Charles" provides a good reason why those so inclined should leave the presidential portion of their ballot blank rather than vote for a fictitious person like "Pedro" from "Napoleon Dynamite":

I enjoy reading Huckleberries online most of the time, even the partisan comments on both sides while predictable, are often amusing. I did wonder what happens to a voted ballot that has written in "Pedro" (or similar non candidate). 

I called the clerk's office and as I understand their explanation, these ballot(s) are kicked out by the machine and the entire ballot must be processed and verified by a team of three real life folks. This creates a situation that adds time to the counting of ballots.

To some voters, their satisfaction for doing so would supersede the obvious added time to getting results and added expense (which is taxpayer money) of hand tabulation. I myself, after having this information will be leaving the president section blank.