GRJ: It does take some experience or at least study to assemble the voltage/current regulators, which involves such measures as layout, observing polarity, etc.
I'm sure that you or I in a short period of time could teach a forumite to do this work, but not every one wants to spend the effort or, I hate to say it, has convinced themselves that they could never do it. Years ago I taught advanced vessel piloting and the toughest task was to convince adult students that they could learn it.
I suspect that you and I share the same philosophy, that if someone else can do a job, we can too, and will learn in the process. (I must confess that as I age, some large jobs I used to do I'll pay to have done. No longer would I strip the cylinder head and manifolds from a marine engine) But many others do not share this. I'm glad of this, for I made a living by doing certain tasks that others needed done.