Priorities Change

You don't have to perceive all old people as heartless bastards who don't care about their grandkids to understand that certain priorities are going to slip a little bit. Fighting for, say, proper school funding is something you're more likely to do when you have kids in school, or even just have peers who have kids in schools.

That doesn't mean people inevitably oppose these things as they age, just that they will fall down the list at least a little bit.

I'm less likely than I once was to get excited about new infrastructure projects (SUPERTRAINS!!!) than I was a few years ago, in part because, well, by the time they come online I'm going to be not quite as young as I used to be.

Small shifts in priorities as the population ages (and the median age of members of Congress) can easily lead to big shifts in actual policy outcomes.