For photography, they are often essential.
Is that true though?
If I was to go through 20+ years of photos I have taken, I can honestly say next to zero of my favourites were from a hide. I can think of just 1 or 2. Thinking about it, quite a few were from a car though. I'd have thought public "fixed" hides were too restrictive for photography. You have no control of your vertical position for a start which reduces your chance of an eye level shot. You've also got very little say in the sun's position compared to being outside.
As a birder, or a photographer, I certainly wouldn't waste my time going into a verbal war over a hide!