Actually the idea that everyone uses the other repos is a rather cynical view. Actually many many users do not use any but the stuff in main/universe. This is typical for many Educational systems (ive seen a few) that have full ubuntu implementations in them. They pretty much use Main/Universe and never touch Multiverse. Likewise more than a few of the purists that I know of stay out of multiverse in an attempt to stay pure of non-free. But thats all a matter of opinion.