I spent YEARS working at an AutoZone as a manager when I was in college and for a while after. You hear all kinds of crazy crap from the people we would hire. I spent so much time correcting them it was nuts.
You have to remember though, they do not pay SQUAT at O'reilleys, AutoZone, or Advance so the level of knowledge is much less. I was hiring people for minimum wage, max 20 hours a week (these were regional rules not mine) and I just couldn't fill spots with people who knew what they were doing.
My solution? Hot young girls. Even if they **** up no one cares and they always come back to see them, haha.
Even when hiring managers, the hourly cap was HARD set at 13.00 and hour. You aren't going to get ASE certified mechanics and such to work for you, ever, at that rate.
You of course will find the occasional awesome parts guy still, but most of the really really good ones have migrated to dealerships or service writer positions. There is NO MONEY in auto parts labor any more. It's sad, because that's how you get some complete moron telling you you will increase HP with an oil filter hahaah
Long story short: retail chain parts stores suck donkey beans. For everyone, employees and customers.