If you could build 10 big houses and sell each for $500k, or build 15 small houses and sell each for $250k, which would you do?
It's logistically easier (cheaper) to build less houses too, and governments and neighbors both like high-dollar houses (tax money and raising existing property values).
I think we need to get our heads around building owned-apartment blocks and people buying "flats" as in Europe. Those are more profitable per unit at a lower price. We do build townhomes here, similar, but they take up a lot more space per unit than say a 4 or 5 story building.
However, demand isn't really there for these, as people have the white picket fence dream still in their heads. Neighbors don't want them, because they perceive them as "renters" who bring values down, even though it's just vertical townhomes.