1. A guy like mayweather or klitscko in one fight makes more than the entire roster combined in a given year. 2. guys like those already mentioned complain about not enough padding. mma gloves are made to be small so that you will be able to use your hands to grapple. 3.It's already too late for them to join. They'll be considered a beginner and it's pretty much a career change. If you're already successful in the career you are at why leave.