The same reason M$ is so big... the have tons of $$ behind it
Yes,...that's pretty much it. With $$$ they have a LOT of marketing media,...so when someone thinks of trying Linux,...all they usually "hear" about is Ubuntu. For instance,..you try and "Google" something about Linux,..and you usually get several search pages full of references to ubuntu. Seems like only those who have been using linux for awhile, and have done some real searching on their own, find a real jewel like Vector.