I don't go to too many concerts anymore, but it would be nice to be able to get a pic or two to remember the event.

Still I understand why they don't let you. Put yourself in the performer's shoes. Can you see why you would not want a bunch of people out there snapping away and later selling pics of you? why should they be making all kinds of money on you? All the while, annoying the decent folks who paid good money just to come enjoy the show.
I can get that.

Plus if there are millions of photos out there none of them are worth a dime and the artist has no control over the really ugly ones.