> People starting families don't just want a house, what they want is enough space. Mothers want a yard they can send the kids out into when they need a moments peace, closets to store everyone's junk, and bathrooms big enough to walk into while pregnant

All of this also means said mother can't go to the corner to pick up supplies, but must drive to the store. There isn't an abundance of neighbors to help out or restaurants with cheap delivery; everything must be done themselves.

The notion that families require low density is very culturally-specific and a choice more than a necessity. Yes, four people need more physical space than two, but not to the extent of modern suburbia.