lol must be another youngin. What Mooner is saying is that they are keeping them hostage so they don't go out and tell everyone who won or that they lost etc. <---that's UFC's reason.
Fighter's reason is that they can train with the pros. And yes, they will fight again. You never know when someone might be injured and they place you back in. Look at Ryan Hall for example.
Many many reasons why someone would stay. Free mansion and free food and free training from the best is enough to stay. But you're too dumb or young or both to understand. Oh look a white belt. Tell us what made you become a fan or sherdogger? How long have you been watching UFC/tuf/mma?