A nation dividing itself into have mores and have lesses builds different sizes of housing. These graphs, which I lifted from Catherine Rampell's blog, show the divergence in housing unit sizes. Simply put, if you can afford to buy a new house, you'll buy a larger house. If you rent in new construction, it will be a smaller apartment than you could have gotten at the peak of the real estate bubble.
Why do people want or need larger homes? (Cue George Carlin) My concern is that people buying certain spaces to satisfy the lurching demon of resale value. I regard this as dumb, particularly when an extra room is designed in a way that doesn't allow it to be repurposed as something useful--i.e. turning a dining room into an S&M dungeon can be a bit of a challenge.