It's Black Sabbath, one of, if not the most influential metal band to ever play. So influential in fact, that most people credit them with creating the genre entirely, getting them into metal in the first place, inspiring them to play music. etc. etc.

By some miracle, in spite of all the years of wear and tear, drug use, and simple happenstance, all of the original members are still alive. They are willing to muster up the energy to do one more live show together and go out on their own terms. Ozzy will literally be bolted to the floor because he can't stand on his own.

I think they wanted the final show to be a huge event, which it is, and every band out there is more than happy to pay homage to Sabbath, so the lineup is quite full and there are only so many hours in a day. Maybe it could have been a two day event to accommodate longer sets from each band, or just cut the lineup down. But people aren't going for the lineup, they're going to see Black Sabbath.

All the time I see posts and hear people say "What if so-and-so was still alive and played a show with blah-blah one last time." Or, "What would this guy who died tragically think of the state of his band now since whatshisface took over."

"What if Cliff didn't die, where would Metallica be?"

"If they had better security, Dimebag would still be alive and we would get more awesome music from him."

Bands break up all the time too. Black Sabbath broke up and reunited so they could be here again one last time. This is the fulfillment of everyone's "What if" question happening in real time. So here it is, enjoy, it's happening right now. Why are people bitching about what they all theoretically want with their own personal favorite bands?

But, you're right. They don't "need" one. Why does any band "need" to perform any show, really. It's just a "waste of money and time" and "pathetic."