Pretty clearly rap comes out of a folk tradition, or rather, a combination of folk traditions. Whether people like particular examples of it, or even the whole genre, is irrelevant. "Folk" isn't another word for "good", still less for "pleasant".

There are folk traditions in which the central element is passing on songs and music that has been formed already, and traditions where the central element is improvising within certain recognised patterns, verbal or musical. The two elements - continuity and innovation - are always present, but the balance can be very different.