Originally Posted by MCS
I believe the short version is that bad players go broke more quickly than in other games, so it doesn't maintain a pool of fish.
Bad players go broke quickly and come back less often, the games play too slowly, and there is less action. Plus some players get very upset when they lose a large amount on the turn of card, while they don't mind losing the same amount in a much longer period of time.
Also, when some players get ahead, they'll quit because they're afraid they'll lose it all in one hand. While in limit, they might make sure they quit a winner, but at least they won't stop immediately.