Major labels aren't the ironclad barrier of entry to a successful rap career that they once were, with cult heroes like Tech N9ne making millions and Macklemore & Ryan Lewis ruling pop radio on an independent label budget. But those were long-building coups, with the artists finding their audience without the help of the RIAA. Drake and Wiz Khalifa built up huge fanbases before signing to their current labels, with many at the time claiming they were making a mistake by not staying independent.
Given the kind of success they wanted, though, they made the right decision. It's hard to imagine Drake having the same chokehold on the rap game without the Cash Money machine helping him corner the radio market. If Wiz had stuck with just Rostrum without an Atlantic Records co-venture like Mac Miller, he'd probably have a respectable career, but probably not a #1 single or a gold album.