I didn't say it made it sound good. I can hear how over-compressed the crap on radio is, and I don't care for it either.
However, if a dim-witted music exec listens to a few soon-to be released tunes, and has to turn up the volume knob a few clicks to hear one of them, do you think he listens for the breathtaking dynamic range on the song, or jumps on the cell to the mastering engineer to yell at him for releasing this quiet-ass disc?
Also, even skilled ears will often interpret the louder of two similar sounds as "better," at least temporarily. So the buyer listening to samples of music will be superficially impressed with the louder tracks. He or she may get a headache from listener fatigue in twenty minutes, but they will never know enough to associate the pain with excessive compression.