With The Sims being up to version 3 so far, I feel like customizable housing should be a fairly standard concept by now. Maybe not to the same breadth and detail that The Sims goes into, but with enough options that every house doesn't feel like a carbon copy of each other.
Because whether or not you enjoy customizing, there are plenty of people do. And it's an amazingly innocuous time sink. Look at the hair style threads and the amount of customization they'd like to have. Various styles, colors, lengths, highlights...
Between hair, housing and
Triple Triad people would hardly have a reason to leave the cities (or the game). Unless it was to get more cards, or to power up those cards.