So many people vote against their own best interests because we are animals, and although we are capable of rational thought, we (humans) make choices mostly based on emotion which is NOT rational. most people think hat just because we re capable of rational thought that we are rational beings. We have not yet evolved to that point yet and probably wont' for quite some time to come.

I always liked the back story in Star Trek of the planet Vulcan, where they were a war like people, who came to realize that only by use of logic and abandoning emotional thoughts and decisions could they really flourish and prevent self destrution. It is an obvious allegory of real world humans, and the general direction we would need to go if we aren't to risk destroying ourselves.