How do we decide who to give mansions? Especially if the "finite" is real and it never comes back. Then you can virtually always make an argument for waiting. When you're literally immortal, there's no such thing as the perfect time to use an irreplacable resource. If you wait long enough, it's basically a lock that somepony better will come along, if not this millenium then maybe the next one.

As for eugenics: Dragons take up a hell of a lot more space than ponies.