I'd say it's because of the same reason why some people vote against their own best interests (e.g. less taxes on the wealthy). They believe that one day, they

I'd say it's because of the same reason why some people vote against their own best interests (e.g. less taxes on the wealthy). They believe that one day, they will be rich and powerful, so they had better not vote in things that would affect them when they get there. The problem is, most of them never get there.