They do tend to be more predictable and set-in-their-ways, yes, and there is also (obviously) more than a bit of racism/sexism/classism involved. But also: that demographic tends to donate to political causes, more. And when a politician retires or gets defeated and wants to get a job as a pundit or on some nice cushy board somewhere or teaching politics at a college or something, those middle-aged-middle/upper-class whites also tend to have the nicest positions to offer a candidate that they like/approve of. So even when EVERYODY votes, there are multiple reasons to cater to that demographic. But when everybody votes, there is at least one countervailing reason not to cater to them TOO much, because you do need at least SOME response from the rest of the population. If you know that most of the rest of the population isn't going to vote ... well, there's no reason at all to consider their opinions, is there?