I work at the front counter at an auto parts store...oof some of these stories make me shake my head.
I think what a lot of it is, is the simple fact that not too many people with mechanical experience want to work at a parts counter. I work for one of the good ones up here in the canada, but i can't imagine most places in the states paying their staff all too well.
I wasn't ever a professional mechanic, but i have done my fair share of wrenching, and I worked as a licensed rv technician for most of my adult life.
After 15 years of that i decided i had my fun, made my money, so i quit while i was ahead with all my fingers still attached. Applied at this parts store and basically got hired on the spot based on my experience.
While I do know the difference between a spark plug and a ball joint, there is still some stuff in the automotive world that I do not know. If a customer has a question that i don't know the answer to, i'll straight up say that I don't know.
...on the other hand sometimes the customers can be a good bit of fun. The other day someone came in needing valve cover gaskets for his "chevy 350"
Me: "Ok...what year is this engine?"
Customer: "doesn't matter! Its a chevy 350!"
Me: "what year-ish? 70's? 90's?"
Customer (becoming a bit aggrivated): "JUST A CHEVY 350!"
So I just punched in an 80's chevy truck with a 350 and gave him the valve cover gaskets for that.
He came back in the next day saying they were wrong. I told him they were for a chevy 350 so after a little back and fourth i find out he had a 1996 chevy 1500 with a 350. I got him the right ones and he was much more polite about it than the day before.