Why I work for myself(NRA certified pistol instructor) is because most of the guys at the shops don't know squat. Had one guy at the nearby shop shoot himself in the kidney and die, while it was unfortunate, I knew the guy and he was a piece of work. I'm staying steady at between 30 and 40 students a month, use a private piece of property okay to shoot on (70 acres) sometimes, other times indoor ranges. I get a lot of recommended clients because I'm A) polite, B) patient, C) not full of it, D) and willing to admit I don't know everything (I got to finally shoot a S&W MP 9mm that was real nice).
Gun shop guys always seem to know more than me but are far less capable. I just tell everyone not believe what a salesman tells you, do your own research.