Yes, making them look cool and mysterious is one of reasons why most of musicians preferring sunglasses. The sunglasses will bring them the cool and mysterious appearance which is always regarded as the accessories to improve the looks. On the other hand, fashion can be another reason, for there are many different styles of sunglasses, which will make them seem to be unique as well. What's more, by wearing sunglasses, it will protect their eyes from the strong lights even in the room. By the way, if they go outside, sunglasses can just protect their eyes from sunlight and uv rays. Therefore, no wonder why most of musicians prefer sunglasses.
I have the same question too. Maybe they just want to look cool or just want tp match their temperament with the sunglasses. Anyway, most of musicians look great in sunglasses. Some of them look really rock with sunglasses that make them more attracting. Still, there are some of them look really literary with full of imagination. If you like it, you can also buy one to enhance yourself.
A lot of musicians prefer to wear sunglasses to show their cool character. As the good accessories, the sunglasses will bring people the cool character. At the same time, the sunglasses will make them look mysterious. You could also protect the eyes from the strong uv rays and other bad lights.