It's too easy to be good. I've already made the claim of how the addition of clapping in pop songs is unfair. Because it's contagious. It gets you into a groove without any work at all. The beats behind rap music are an exaggerated exploitation of this effect. Boom. Boom. Boom. Boom. Boom. Boom. Boom. Boom. You're in. Before any words come out. Before any melody. They have you. You're grooving. So, regardless of what comes next, people already kind of like the song. So, the path of least resistance says I'm going to throw some crap lyrics in that rhyme with club, bling, dope, lady and call it a hit. It's too easy for rap music to be good, and therefore, it's rarely great.