Obviously cars are useful, but we've built our cities to maximize that (and we still spend a lot of time stuck in traffic, even so). That doesn't mean that there aren't more useful possibilities, just that the inertia in the system makes them seem like a dream.
The problem with your analysis is that your concept of “useful” is based on a set of priorities in your head that’s almost certainly not shared by the people who prefer to live in car-optimized areas. Cars let you travel in private, on your own schedule, without having to interact with other people. You might not value those things. Lots of people do.
Just about every UK suburb is walkable to train station a supermarket some smaller shops and probably a pub somewhere.
I the US the sidewalk just ends and walking can be quite dangerous in places.