While there is validity to all of your comments, I can't help but believe that the main purpose is to keep the price up and create an exclusive environment.
Dupont sells, directly to the public, Imron catalyzed polyurethane, a much more dangerous to the user substance, and they don't seem to worry about the legal implications with that.
Their concern about warranty issue and backing their liscenced fabricators and installers is legitimate and appropriate. I just believe there should be a" buyers beware" market for the DIYer.
I've worked with it a little with small scale projects to know, while not without a requirement for skill, planning and knowledge, it is not rocket science.
Frank