I think it has a lot to do with the fact that a lot of them have day-jobs to go with their athletic careers. Once the sport becomes big enough that they all become full-time athletes and make tons of money in the process, they'll be more like other athletes.
Good for Reza. Sounds like the kind of situation that can turn real bad real quick.
I disagree. I think most UFC fighters are full-time athletes already, and the real reason they are the way they are is because martial arts and the toughness of fighting produces traits of respect and humility amongst its practitioners.