Well because it's an e-fed really, the point of it is for people to create their own characters. I do support the occasional guest appearance of WWE superstars from time to time. Maybe even have the superstar temporarily compete for a month or so, like John Cena doing a feud with a superstar in the company, and then leaving shortly after.
Of course if one of the users wanted to use a WWE superstar as their full time character, that would probably be accepted, but really it doesn't fit in with the e-fed theme.
That's why there is a booker section, and an e-fed section really.