I feel like both justify the other in some ways: I need a car to do big shopping trips <-> I need to do big shopping trips because I have a car Or, as you say,

I feel like both justify the other in some ways: I need a car to do big shopping trips <-> I need to do big shopping trips because I have a car Or, as you say, having a car is just a given most places in America, so there’s not really a question of it being any other way.