Pretty much this. I don't get that obsession either, there was one mount I actually liked enough to run extra dailies to farm their rep (Valajar) and I didn't mind it, and other than that it was just a suprise reward for doing dailies.
But the obsessed collectors who feel "forced" to farm everything, just for the sake of having huge collection of mounts they will never use anyway, are really whiny as seen in this thread.