They're out there, just not in huge numbers. Count me as an Alternity lover, before d20 came in and stole our hearts, had d20 not become as prevalent as it did, my group would be playing Alternity to this very day...
It was a very good rules system, with plausible and playable damage rules, armor and armor penetration rules, and some jam-up source material. I ran a Star*Drive Campaign about a Renegade Bill Gates Artificial Intelligence that my players enjoyed immensely, and we were as of Winter of 1999/2000 even working on a Fantasy Alternity Rules system.