Brands discovered the hip-hop market
Brands were aware of the following that rappers were bringing to their products, but while some try (and still do) to stray away from that audience, labels like Cross Colours aimed specifically at the urban market. Athletic brands like Starter, who was already huge in the '90s, enlisted guys like DJ Jazzy Jeff to model their gear, resulting in some of the best hip-hop fashion ads of all time. Drink companies like Coke caught on, enlisting guys like Kris Kross for Sprite ads.
Today, it's a marketing demographic that's been boiled down to a science. Graffiti-style typefaces and mock-rap beats are engineered to give commercials and products street cred. It's a world where Rap Snacks exist and Nas is doing Gap ads—which is why it's such a breath of fresh air that rappers like Kanye West and A$AP Rocky are helping to redefine hip-hop style for a new generation. They're making sure the sartorial vernacular of the medium is defined by the culture, not stereotypes.