I think the "how many people can do it" part is where things go astray. "Can" can mean "are capable of doing it" or it can mean "allowed to do it" and those are

I think the "how many people can do it" part is where things go astray. "Can" can mean "are capable of doing it" or it can mean "allowed to do it" and those are conflated under the current system. Plumbing is maybe a good example, in the sense that if I own a home and feel comfortable with something, I can do whatever repairs I want. I could hire my friend John Smith to do it if I trusted him. The limit is the inherent risk I take, and knowing that if I screw something up, I could cause problems that cause problems to me. There are code issues, but that gets complicated and is orthogonal to the issue of who does the work that meets code. In healthcare though, even if you are entirely capable of doing something yourself, you are not able to legally. If there's a medication that you have been taking your entire life, and has been deemed safe in the primary scientific literature, you are still not able to just go buy it from the pharmacy without a prescription. If you want help or advice with the medication, you also can't just go to a provider that you want. You can't take the drug yourself, under the advice of the pharmacist for example — even though the pharmacist often knows more about drugs than an average physician — and you can't take it from a different type of provider that you trust more, for whatever reason.