Whether to mute or not to mute is a matter of taste and style. Some folks don't like and so be it. However, as has already been discussed quite well, muting is one of many useful and powerful techniques to give texture and punch to one's playing. Thom Bresh, the son of Merle Travis, and Comer Mullins, a National Thumbpicking Champion, are true masters of the guitar, as are others named earlier in this thread, and can perform lengthy sets with no other instrument but guitar, and give each piece a unique treatment. They use technique to give each song or tune whatever it needs to become alive rather than fit the music to their playing. They play music rather than use music to show off their playing. When a person opens the mind they open the door to greater possibilities and new dimensions of musical presentation.