I've never been to Japan, and have never really asked anyone who's lived there, but from memory, I recall reading that like 90% of the population lives in urban areas and most people there probably live in apartments.  If I am incorrect on this assumption, then this post is invalid.

Anyway, it's interesting to see the number of people in anime living in nice spacious (Western style?) houses.  People living by themselves seem to prefer apartments, but families are almost always in two story houses.

Trying to show ideals?