As more and more competitive players join the play group at my shop the less overall players I see. And many of the competitive players seem to want to play competitive against casual players, not other competitive players.
The casual players are my backbone. Eventually the competitive players (who really are just sore losers, and mostly learned how to play Commander and not Magic... but that is a whole different issue with the game) tire of not being able to steamroll casuals, or get tired of actual cEDH players curb-stomping them and stop coming.
I tell players, "it is easier for a competitive player to play casually, than a casual player to play competitive."