Oddly enough that's the way it used to be, doctors were doctors because they said so. Although, if you had a friend sew up a bad cut and you gave him twenty bucks for his trouble I doubt the police will come knocking on your door. I suppose if your friend decided to do it as a business off his front porch I'm sure somebody's bound to come around at some point.
Well, it's actually not a free country in this regard. It's illegal to pay some guy with good hands but no degree to do it for him.