I think rynne really hit the nail on the head. Seeing the goal of playing music as making something new, groundbreaking, and original just doesn't take the whole picture into account. Lots of musical traditions have very little regard for making something new and groundbreaking- I play old-time and texas-style fiddle, for instance. Most of the musicians that play this kind of music seek not to innovate, but simply to perform it live, often at a square dance or somesuch. The same is true for many kinds of music. There are lots of bands out here in the midwest who just perform classic rock hits in bars for the free beer. They're not amazing musicians, but they are usually friends, and they have fun.
MOST bands feel no need to artistically justify themselves, I think. We just happen to follow the ones that do, because we like being on the bleeding edge.
Anyway Caspian, for every ten (ok, maybe 100) shitty bands, a good one will come together, giving us something new and original. It's not that hard to filter out the bad bands, is it? It's not like there aren't enough people on the internet jonesing to tell you what's worth listening to and what isn't.