One must wonder if the therapy works if it's as trivial and simple as you say.

Rarely are these things straightforward and clear cut.

That being said, I recently broke my ankle, and found that the protocols still often include 6 weeks off it, despite modern evidence largely showing zero downsides (and some benefits, especially in terms of early recovery) to weight bearing immediately - Probably costing possibly billions of dollars in lost productivity and unnecessary PT every year.

I probably shouldn't get too high on my horse about random unexplored therapies - plenty of things in medicine that are just done some way because that's how it's always been done.