Why has pop and rap music dominated the charts for such a long period of time?

It would seem the mes are much more attune to reheating the left-over pizza from last night than hearing something new and unique. Music as an ideal is an expression of one's soul. At the very least, music is a personal communication from oneself to many. It is intended to be a form of art that captures an emotion or relates an experience - to further understanding and compion. Historically, music expands and grows - always searching for something new... For some reason the last decade or more, most music on the airwaves is no longer creative - no longer an artform - no longer an experience - no longer music... It has become a commodity like buying a gallon of milk at the grocery store. What happened? Why are there so many bad musicians that further this cause?