Why vote?

Re: paragraph on why it's not rational to vote, cited in Library of Economics and Liberty article: Economists who lack an imagination by Scott Sumner

This is the paragraph:

4. Economists who say that voting is not rational because there is only a tiny probability that your vote will swing an election.

This is why I vote:

1. I've seen bizarrely close elections in my life. I know it's important to cast a vote, so you don't feel guilty at the result.
2. What do you think happened in France a few weeks ago? Right wing won because majority didn't bother to vote. The win shocked more citizens into voting, so the right wing lost the subsequent election. 
3. My dad used to say it's better to flip a coin than not vote. He had some statistical argument for this, which I can't remember, but it may have been: at least it builds the impression that we're paying attention.