The intention behind statutory maintenance is supposedly safety of course. For this reason they exist on cranes, lifting gear, pressure vessels, release valves and so forth. it is also the reason why they are so prevalent within the underground coal industry.
High voltage equipment operating in an environment of highly explosive gases tends to be a little hairy at times, so the statutory tasks are there to help manage these risks safely.
That's all well and good; and on the surface it seems like a great idea. Unfortunately it is the implementation that has gone awry in most cases. In some cases this is merely counter productive, but at times it is actively increasing the risk of the type of incident they are supposed to be protecting against.