[2021] Why can certain things not be wall mounted, only frame mounted?

It was before my time on the project but I believe the intent was you place things on frames, and walls were used for covering up cables and pipes etc. The problem with placing stuff on walls backed by another wall us stuff would collide because of how they're designed so you'd get placement issues but not be able to see what they were being blocked by. As for making devices fall down if you deconstruct the frame underneath, well I think there would be riots :P