I don't get it...Why the hell do a band a big, wealthy, "popular" as Metallica need to do this? Oh, wow! Their losing, at most, what? 1 million? Com'on, this is pence to these guys! What else for then? Artistry? What, people are listenning to their music aren't they?...Why then...the quickest answer is greed, simple....
On the other side of the coin though, there are perhaps (minor) infrigments on some kind of copyright, then there simply personnel standards...but, unless I'm wrong, didn't Metallica used to endorse bootlegging of their gigs...hmmmmm.......

Was an attempt to give both thoughts, but urrr...I think my own are pretty clear....