In my travelling career, I have seen lots of no photography zones, but the reasoning behind it mostly made sense. It is related to national security (infrastructure, proximity of military bases) and museums (copyright issues and/or light-sensitive works).
However, I have seen also places where I could not justify it. For instance, recently I was in Jeita Grotto in Lebanon. They have a no photography policy that it is so strict that they require people to leave cameras and even mobile phones in a locker prior to entering. The cave is amazing, and it is a pity that I could not take any photos. And I still do not understand why, there is nothing sensitive inside. And it's not like I wouldn't go there if I had seen the photos. On the contrary, it would encourage me even more to go there after seeing the photos that other tourists took.
Why do some places have a strict no photo policy?