Or, they live in one of the 40-something states where the election margins are large enough that it doesn't matter whether they vote.

My state hasn't voted Democrat since 1964. The only two elections with less than a 10-point spread since then were in 1976 (7.5% spread) and 1992 (5% spread due to Perot stealing votes from Bush Sr.).

I moved to this state in 1993.