The reason for not having flash would definitely be the fact that it can damage what you are photographing, but I'm not sure why all cameras would be disallowed outright. It's probably a way to get you to buy all those print and postcards in tourist areas.

The culture thing is also feasible. When I was in Guatemala, many Mayans will refuse to have their picture taken, since they believe it will trap their spirit. No cameras or recording devices of any kind are allowed at their ceremonies, either.