Yeah, getting tested is an invasion of privacy, but being photographed nude isn't? Makes perfect sense to me. If you're crazy.
Not to mention the liability ACs would be incurring if they didn't test for illegal drugs and a fighter was injured while fighting under the influence.
Not only that, it helps many people with stress--although it actually causes anxiety in a large population of daily users--and can act as a pain reducer dealing with routine muscle-aches from training, etc.