Read other letters about this article
And ultimately I found one: leadership. Sure, my vote individually doesn't accomplish much, but by virtue of having cast it deliberately and with forethought, I gain a (very) small amount of moral authority, and lead by example. Every little bit of motivation helps other people get out to the polls. If a lot of us are leading by example in this way, it drags other people along who would not vote, and that does help the process work properly.