True, but that only exists because people film and share it. The key thing is to manage it so you aren't intruding on other peoples enjoyment and balance with your own. I've filmed plenty at shows over the years and enjoy watching my footage back, though I always attend multiple shows so ration it across the tour and only film when I can get a clear shot below my eye-line so as not to block anyones view. Those clips go on youtube for people to watch if they choose.
As for a GoPro, I have seen them occasionally at gigs. One at a Taylor Swift show got stopped about 10 minutes in (back in the