Live music is like the movie "Chicken Run." I never feel motivated to watch it, but once I do I'm surprised how much I enjoy the experience.
Some would say that live performance is definitive, that recording and replaying is a hollow, lifeless imitation. I'll save that intellectual position for the guys at the poetry jams who walk up to the mic and say "this is not my voice, this is an electronic interpretation of my voice." Those guys would know better about the supposed purity of live performance, and are more comfortable being immediately disliked.
But there is something special about seeing someone play their own music, and I don't know that it has much to do with the sound itself.
-As with sports, martial arts demonstrations, and dances, being reminded what human beings are capable of is pretty incredible. When you listen to a recording, that simply doesn't register the same way: you are dealing with the sound alone, not the sound and the person making it.
-It's hard to be a jerk in person. When you only encounter the art and not the artist, you can be more critical. Listening live robs you of that emotional distance.
-Watching someone sing their music, like hearing a person read their writing, lets you in on the subtle inflections and body language they use. A lot of people say that Citizen Cope, for instance, doesn't write enough lyrics, instead endlessly repeating his choruses. It wasn't until I saw him live that I realized he uses lyrics like a mantra, a point of meditation that he repeats in a trance state.
But not all art forms have the option for live versions. There are book readings, but they aren't common. Movies and TV let us see the actors involved, but no one else, and since we're not in the same room as any of them it isn't the same. Even in a restaurant, the chef generally stays in the kitchen. Music, then, is fairly unique in that we have so many opportunities to encounter the people responsible for it.*
*Unless you count Twitter.