The Freakonomics podcast referenced upthread does mention earthquake codes and some other factors that have helped lead to houses becoming disposable. Nonetheless, I'd note though that it's not really the case in, say, the Bay Area. It's a behavior that seems to have evolved beyond practical reasons to become a cultural pattern.

There are also good reasons to junk old cars but it would be pretty inefficient if it became a societal taboo to drive a car over five years old or to purchase a used model.