Too bad we don't know when they will pay off. A friend of mine just bought a house for $250k from someone who bought it in 1998 for $70k - 6 months before selling they refinanced for $225k. (this is all public information if you go to the right courthouse - he knows this because it is in the title).

Which is to say there are some people who don't have their house paid off yet, but will have it paid off before they retire, and then live rent free (but with other bills and taxes). There are other people who will not have anything paid off.