I'm sure ill catch some chit for this from the big brother hating liberals. Licensing, prerequisite and mandated continuing education... I have been at our state Capitol all week testifying and crafting such for my industry..
Consider yourself in catching mode.
The very last bunch you want involved is the poor customer service people aka the gubmint under the guise of protecting this or that they will destroy it all. You'll get all kinds technical requirements from lots of experts and damn little in the way of customer service skills. Both are sorely needed and very hard to come by when dealing with heating devices in a home.
Take a really good look around at the mish mash of codes and requirements already out there for other "professions".
To answer the OPs original question yes, someone has to do that which someone else isn't willing or able to do on their own or in the alternative maybe those that can't or won't shouldn't have what they have.
Perhaps a case to point out where I'm coming from is in order, a Nurse now well on her way to becoming a Doctor bought a house and in it was a forced hot air furnace. You know those things that you set the t-stat for and have on auto fuel delivery (out of sight out of mind). Evidently it had never occurred to her that they needed regular service and especially cleaning, after things not being too warm for a long while one day she called a freind asking what to do. The answer was to call a heating system company for service. She had been in that house for several years before even one person serviced the furnace, it had enough dust and dog fur in the system that it was a wonder it ever got to turn off.
The OP is also right that there are a lot of DIY folks on here, while a lot of us just like doing things some of us are also cheap and know how to get the blood out of that buffalo on the nickel (and likely a lot of other animals as well).