The last time I was at a crowded museum I spent roughly 20% of the time just trying to avoid getting in the way of people taking pictures. Everyone was taking pictures everywhere of all the installations. I considered doing so too, but realized 20 years too late that there are far better photographs of a work of art (or at least enough) by professional photographers with different takes/interpretations than I could do without decades of training (on average). If you like a piece, there's nothing to stop you from buying a print or downloading a picture. I get it that some people do it more for remembering "that time I saw it in person" instead of trying to capture the essence of a piece, and that's fine (that's why I used to take the pictures), but multiply the amount of time it takes to do that by every piece you come across, plus how much posting it on instagram/whatever/facebook removes you from "the zone", and I think it's just a different way of massively disrupting your attention when the MAIN reason you're there in a museum, for a limited amount of time, is to suck it all up. I'm sure many people don't get distracted by trying to take photos of all the art, but once I stopped and just focused on concentrating and nothing else, a trip became much, much more enjoyable, and even memorable.