The music is part of the character of any game.
However, I turn off the UO music for one main reason.
If you're staying in one area, doing something, the same track will loop and loop and loop.
When you enter an area, the character piece should play for the purpose of establishing the scene. Then, when it's finished playing, it should go away.
If it doesn't, it becomes as irritating as the swamp ambience.
Edit:
Also, the comparison is not a good one.
Stones, by its nature, is a humble character piece. While Shaping the World is far grander, and more impressive.
Without a personal preference for Stones, people are more likely to go with the piece that is more inspiring