I've never understood why people want such massive houses, especially since most people aren't home all day. I see it as just more rooms I'd have to keep clean. But maybe people want space at home because when they're in traffic or shopping, it seems so crowded.

Its simply a matter of what sells. In a place where even a small home is 200k because of school fees and other fees a 2000sqft home may be 225k and a 2500 may be 265k and the 3000 may be 300k.

As for why have such a huge home?

Well for one thing the bedroooms tend to be bigger the bathrooms tend to be bigger and you tend to get extra rooms. Rooms you can turn into entertainment rooms computer rooms playpen rooms hobby rooms and of course that ever important where to put all my old crap rooms.