Studios are creators, just like publishers are integral to the creation of a book. Why else do so many hiphop and pop acts prominently mention their producers?

Studios are creators, just like publishers are integral to the creation of a book. Why else do so many hiphop and pop acts prominently mention their producers? Besides managing the production process, labels are also investment companies, who take all the risks. How much did Courtney Love pay upfront to get the album made and the tour organized? Also, hundreds of thousands of independent musicians offer their music directly through iTunes, or via a cheap intermediary like CD Baby.