I think the WWE model is based solely on business and demographics of their main audience (North America minus Mexico). They have their rosters in somewhat representative numbers.
There is a 10-15% minority of blacks in North America
-> There is about 10-15 minority on the WWE roster (Lashley, Benjamin, Ron Simmons, Viscera, Corvon, etc.)
There is a 10-15% minority of Hispanics
-> 10-15% in WWE (Carlito, Chavo Guerrero, Mysterio, Super Crazy, etc.)
There is a 5-10% minority of Asians
-> 5-10% in WWE (Batista, Jimmy Wang Yang, Funaki, etc.)
60% white in N. America
-> 60% white in WWE. (HHH, Cena, Orton, JBL, Flair, etc.)
Even Jews get proportional representation with Raven and Goldberg (neither are currently in the WWE though). Amazing for an "entertainment" avenue for realistic representation (numbers-wise) of this group.
The one demographic that used to be heavily represented was Native Americans (even though Chief Jay Strongbow was really Italian, among other ethnic fakers). That has dropped since Tatanka's run. Some guys look semi-native, like Paul London.
Polynesians have also been heavily used. But since they are, on average, a physically huge group, it makes sense. They seem 'made' for stuff like football and pro wrestling.
Other minorities:
Muslims -> Sabu, Daivari
South Asians -> Great Khali
The one thing I could atrribute it to is Vince McMahon's and wrestling's bad relationship with good ol' MSM and their irrational ethnic quotas. Vince is even seen ridiculing MSM in recent RAW episodes. USA has always been kind of an outlaw network, so WWE fits in quite well. Of course UPN/CW Smackdown! has always been a little less white, but not to a great degree.
Edited by: FieldThrower