I've no idea what you mean when you say "cities have unlimited housing". Should we just bulldoze everything and build skyscrapers, is that your idea of a good city to live?
I don't know about North America, but replacing everything with skyscrapers is simply not the least bit desirable in the vast majority of city centres in Europe, for example.
A city of skyscrapers would also make a pretty dystopian city, the way I see it.
Density increases innovation. Density decreases travel carbon emissions.