Being a blogger and a netizen, I have observed on several web forums/communities that music has been categorized often as an ‘entertainment’ in the drop-down lists. While there are many that consider music as an entertainment, there are also, others who consider music as an art.
Entertaining music need not be artistic enough and art music need not be entertaining enough. Do listen to the differences in compositions and playing styles in classical music and popular film/pop music and you will understand what I am talking about.
It can be inferred from our cultural mythology and literature that this difference in the entertainment and art components of music could be a result of our inability to deal with boredom.
Here's a possible reason that explains many great musicians are unpopular due to their inability or a lack of interest to amuse and entertain the masses with their music.