The mainstream majority listeners who want to hear their favorite hits over and over again do not want to believe that they are closed-minded about music, even though they are. They want to be told that they're listening to a wide "variety", and hearing "anything" and "everything", because it makes them feel as if they are open-minded and adventurous, although in reality, if something they didn't know came on, or something in a genre of music that they didn't identify with, their fantasy would end for that station, and they would turn the dial looking for more of their favorite hits elsewhere.
These "adult/variety hits" stations that say "we play anything" (The Harbor) or "we play everything" (the former Mike-FM), and then play a very narrow, repetitive playlist of mainstream hits, pander to this psychological phenomenon more effectively than any other format.