The easiest explanation is that hip-hop's biggest American stars, such as Kendrick Lamar and Post Malone, are more established and are less focused on churning out hit releases than they used to be.
The 2018 Pulitzer Prize winners were announced earlier this week. Among them was rapper Kendrick Lamar. He is the first musician who is not a classical or jazz artist to win the award. He will win $15,000.