You don't need to understand those. The practical side is this: You can ask someone who does understand. The less practical reality is that the people who created the layer didn't have what it takes. (skill, time and/or money)
> programming as a profession would benefit from professional licensing
The existing solution is really quite simple. You have every layer up to the wall socket done by licensed professionals. Then you let those without formal certification go wild plugging things in, wiring extension cords, lamps etc. When comfortable with that they can even lay some pipe, pull some wires in it, add switches and wall sockets (As long as the components are certified!) All the way up to the fuse box (and no further!) They can even wire their whole house provided someone with certification signs off on it.