It has to appeal to the least common denominator to have the biggest chance of selling the most units ... it used to be whole albums (LPs), now its singles, or full blown video spectacles where the music is not as important as the distractions of pyrotechnics, flashy lights, scantily clad choreographed dancers, etc.
As long as an enormous chunk of the music buying public just wants something they can shake their booty to, or so Susie Homemaker can hum along to something uplifting while she's making dinner or housecleaning all day (< that is my Mom to a T!), or the management of a store that wants to make everybody that comes in comfortable enough to spend their money there ... they're going to stick with sounds that are safe, and don't make people think too much, or offend their delicate sensibilities.
Barf