I remember four or five years ago everyone was searched at most concerts and you had to take your cameras back to your car. When I was at the U2 concert a few weeks ago, pretty much everyone had a camera, and a lot of folks even had video cameras and no one cared.
It’s come down to an unwritten rule (often, sometimes actually written) that cameras without removable lenses are permitted. We got here because EVERYTHING is a camera now (phones especially). But unlike a film camera, digital cameras have those bright back panels that can be disracting to the audience members in back.
Alternatively, I’ve seen several performers who know the cameras are out there and that venues have gone smokeless so lighters aren’t “allowed” and will have the “light show” from the crowd done with cellphone cameras now.