There are 1-2 market taking shops that dominate. There are many market making shops. Market making is not a winner take all environment because where you are in the queue determines when you get fill information which will sometimes put you ahead or behind other people. Also, the strategy is more vague. It can be defined as "sit in the market but try not to take toxic or informed flow". Many different trading profiles can accomplish this. When you are market taking the strategy is more "cross when the market is about to move". Lots of moves are initiated with rather simple and easy to understand triggers. The problem is that with everyone doing the same thing at exactly the same time there's more of a winner take all phenomenon.