I can see that if you live in a city flat with no garden, and traffic all around, there might be good reasons not to let a cat out, even one with good hearing. But I don't think keeping a cat in circumstances like that is really a right thing to do.

Actually I'm inclined to the view that an environment that isn't suitable for a cat isn't right for a human being either - and that doesn't mean no cities, there are plenty of ways of building cities that are fairly cat and human friendly.