It does seem counterproductive to do it that way.Videotaping a concert sounds cool, but if you've ever videotaped something you'll notice that you pay all your attention to your video device and totally miss the concert itself, completely missing out on the fun of being at a live performance in the first place.
Some acts allow cell phone recording--as long as you aren't selling it.
But the quality isn't great-but it can be a way to remember the concert.
And if you do it--still buy their music.