More accessible/better transportation - More people taking public transportation - fewer people gaining driving skills

I know that's why my aunt at least can't drive very well. She lives in Manhattan, has a car, but doesn't use it very often. Lack of experience in anything (for most people, in general) would lead to a lessening of skills in that area..

So perhaps because so many people take the subway in NY, more than say, L.A., they drive better in L.A.?

Well, at least they know how to drive fast enough (ie: the speed limit) to keep up with funeral processions on the highway!