A chance to get together with friends for a bit of fun?
A chance to experience the thrill of seeing an audience dance and sing along, knowing that you're partly responsible for them having a great night?
A chance to express yourself on your instrument, communicate with the audience and, to some degree, show what you can do?
Although I play in covers bands, I have to say, for me it's primarily the third option. Yes, even when I'm playing Brown eyed girl for the 300th time! Maybe I'm kidding myself, but I can't help but see it this way.