It's a valid concern and this is where the free market aspects really come into play.
If a school opened up with the goal of training people to diagnose and treat cold and flu symptoms, so that the graduates could diagnose those symptoms and their severity, then recommend a course of care or call in a prescription...here are the potential barriers.
1. Insurance companies wouldn't pay for it at all because those graduates would lack any type of professional credentials.
2. Those graduates wouldn't actually be allowed to call in prescriptions, also due to lack of credentials.
3. Getting credentials approval would require a lot of money to push things through the process, if at all. Then the school would have to be setup in an effort to recoup those costs. The school would be setup with the goal of making money most likely and everything else in the process would have to happen before the school even became feasible.
Assuming all of those things happen, then insurance companies would largely decide whether or not to even pay for those services and people who had companies that wouldn't...would not likely go to those providers. If they did pay for them and the pay was too low to justify the time commitment of dealing with the insurance companies, additional costs would be involved in terms of staff to deal with billing and followup. (Insurance companies often deny on first request, requiring rebilling).
When it comes to cash flow, insurance changes at the beginning of every year can cause payments to be delayed for up to 3 months which becomes a huge problem for office leases and payroll. Between all that if the compensation isn't high enough, it disincentives people to go into the field at all.
The alternative is pure private pay and allowing individuals to decide, this care is good enough for me. Which would require signing something indemnifying the practitioner from legal recourse since they wouldn't be able to get malpractice insurance. If that care costs more than the co-pay at their regular doctor...they will have no reason to choose it. And even with private pay, those same practitioners still wouldn't be able to call in prescriptions.
That is the industry that has been created by removing health care from the free market.