The thing that confuses me is how there are college head and assistant coaches who are able to retain amateur status while, as previously mentioned, someone who gives a $50 putting lesson is a professional. College coaches are giving instruction - a form of professional advice - to golfers for a salary.
Almost no college coaches are regularly giving instruction, and there are people teaching green reading (AimPoint instructors) who aren't professionals, either. College kids often help run summer camps where they might give "some" instruction… under the auspices of a coach of some kind. There's quite a difference between a golf instructor and a college coach, and I say that as someone who does both. Some of my students are at D1 to D3 schools, and the coaches range from van-drivers to really good golfers… who mostly still just encourage their players to work with the coaches who got them to that level.
Plus, those who think that some pros should be allowed in mid-amateur events and the like should take comfort in the fact that the mid-am ranks are increasingly full of reinstated professional golfers, some of whom made hundreds of thousands of dollars playing the game in their careers.
There are not as many of those as you think, and the USGA/R&A has been re-instating amateurs since the the beginning of pro/amateur golf.