I think a lot of people like the idea in concept but once they actually get out and seriously try to marry it, they get fed up fast. I only run ABS 1 in GT5 'cause I really hate the way the non-ABS brakes feel, it's just really clonky. In Forza the brakes feel awesome so I love, and only run, no ABS there and in the sims I run from time to time of course, much easier and funner to find the sweet spot. So that's my reasoning behind it.
But as far as running no ABS in a league, I really don't see it as a major depature, as long as every one's doing the same thing then it'll be like anything else, more lock ups yeah but it wouldn't make a crazy impact on the racing.