Lawns are a two-fold problem. First, they force you to waste a bunch of land on lawns. In our county, the minimum lot size is about a quarter of an acre. In our pre-zoning code neighborbood, lots are less than one third that size and everything works just fine.

Second, municipal governments make it illegal to actually do anything with that land other than wasting it as a lawn. Can't have chickens, can't plant it, etc.