I guess the big dogs (Tim, Pharrell, etc.) did, but the Rockwilders or EZ Elpees did not. Most of them likely had production companies and were grooming artists, but never the backing of one of the major labels.
I think it also comes down to the fact that a lot of producers don't seem to be all that interested in that sort of thing. They're in the studio making beats.
Granted, a lot of rappers who were given labels probably weren't either (Nas is a good example as he's had TWO labels that have done nothing), but I suspect what happened there is it was offered to them and they shrugged and said "sure, why not?".
___________________________ OL' DIRTY BASTARD on himself: "I may curse, I may have a bad mouth, whatever whatever. I'm not that bad, yaknow'mean. Bad to y'all, I dunno how y'all... I don't give a fuck. Um, I'm a good person at heart, for real and shit.