Reason #2: 2 Chainz already has plenty of visibility without the help of a major rapper like Kanye West.
Say what you want about 2 Chainz right now—he's awesome, he sucks, he uses the same rhyme scheme on every song—but you can't say that the guy hasn't worked his ass off (he calls it "griming") to get his name and his face out there. And, he's largely done that on his own. So, he doesn't really need Kanye's co-sign in order to get people to check for him. He's managed to get plenty of attention for himself. Signing with 'Ye might help increase his visibility, but it also might stunt his growth at this point if G.O.O.D. tries to have a hand in how he's marketed to the public. If you're 2 Chainz, why risk it?