I'm fairly sure it's related to the car culture.
If you compare the US with Europe, it seems to me that people have very different attitudes towards using their cars. In Europe (generally speaking), if something is a 10 minute walk away, people will look at you a little strangely if you use your car. In the US, it seems to be the other way around - people look at you a little strangely if you decide to walk.
I would speculate that this is actually a result of the big status game working a little different in the US and Europe. In the US, there's generally not a lot of subtlety involved, you just show off your big car/home/whatever and that gives you social status (generally speaking). In Europe, there's a sort of balance: to get maximum status, you should still show off your car/home/whatever, but if it's too obvious it may backfire. So back in the day when being able to drive your car was worth something status-wise, a pattern was established. Which then affected coming generations in various ways, including city planning, lack of public transportation etc.