Consider these two clever-sounding game-theoretical arguments side by side:

You should vote for the less evil of the top mainstream candidates, because your vote is unlikely to make a critical difference if you vote for a candidate that most people don't vote for. You should stay home, because your vote is unlikely to make a critical difference. It's hard to see who should accept argument #1 but refuse to accept argument #2.

Yes! This is the argument I've been making in government class for the past few weeks. This disjunction shows that the type of reasons that people have for voting aren't based on a desire to influence the election but are based on social aspects of "being a voter". The reason they ignore third party candidates isn't because they would be "wasting their vote", that's a rationalization. They ignore third party candidates precisely because they're less popular (and have a stigma attached to them) so expressing sympathy with a third party fails to improve the quality of their own lives.

I think politics is almost all social. There's no incentive to betray your social group, even if their arguments are wrong, because leaving will exert almost no influence on the overall power or implemented policies of that social group, and if you leave you'll lose valuable interpersonal connections.