That doesn't mean art has been automated; it means we've invented a better paint brush.

Most cases of people paying to see human performers are of performing already-written music though, so I doubt think that's the drawcard. Actually I don't think anyone truly knows why we obviously gain something from watching live performers that can't be obtained from watching them even on the best quality home entertainment system imaginable (*), but at least part of it is feeling like you're part of the performance, knowing that the performers feed off the reactions of the audience etc.

(*) And why has there never been a market for broadcasting music performances in cinemas?

Watching live piano performances has always been niche. The point is that the player piano didn’t replace them, but moreover player piano concerts aren’t even a thing. The human element turns out to be an important factor here.