They keep him around because he is an entertaining fighter.
So many people on here forget that the UFC is a promotions company, not a "maintain the purity of the sport" company. They want revenue 1st, then to determine the best in the world 2nd.
This is why some guys get cut coming off wins. It isn't all about winning, Jon Fitch proved that, no one wants to see him fight even if he does win. This is sports entertainment. Sports are where the best compete in fair contest and the best wins. Sports entertainment is when the guy with the most buzz behind him jumps contenders who are ranked higher for title shots..... which I am fine with, but more people need to accept this reality or they will continue to be disappointed.