It's because it's very difficult to imagine circumstances other than what we live in. I agree with what you're saying in general but only in general. Plenty of liberals live in small towns and plenty of conservatives live in big cities.
But a LOT of liberals have only ever lived in a big city and a lot of conservatives have only ever lived in rural areas. And for those people, a move is transformative
For the conservative, the idea that government can do anything useful seems insane. But move to a big city where government services form the backbone of your water, sewer, mass transit, snow removal, etc and it's really hard to look at government and say it can't do anything right. Government somehow keeps Chicago clear of snow. Like -- really think about that. That's an ongoing and ENORMOUS project and it goes off largely without a hitch. It's difficult to see that in person and really say "government can't do anything right."
For the liberal, the opposite is true. They've spent their life surrounded by largely competent government. They move to small town America and suddenly the entire local government is run via the good-ol-boys network. Distance makes it all but impossible to actually get services to the people who need them. Taxes seem like they take a lot out of your pocket and don't put much back.
The problem is that our votes -- especially at the national level -- govern both groups.
