Dude Ive said this already. Most people don't care if the sones sound better. They go to the beats and get the beats, just to get the beats. Sound is not a priority for them (most of the time). Also some people torrent their music or copy it from youtube and the quality is sooo bad but it sounds "great" with beats but not so much with other better headphones on display.
Beats try to apoeal to a younger demographic. Kids who get them to look cool and think they have "swag".