So this parts thing...
I work for a national chain, owned by a multi national.
Our parts are bigger and heavier than car shop ones in the main, but the business model is similar.
Customers don't want to pay more than they have to for bits, so it becomes a low margin race to the bottom. Because it's low margin, wages are poor, so most of the staff are too.
My deal is different, but I really feel for the store based peeps. We have over 3600 part numbers in our branch alone, and heavy trailers don't come with online parts diagrams, yet somehow it's their fault if they don't know what particular air brake valve lowboysdotcom used on the customers "It's a 3 axle" version. And then it turns out be a lowloadersareus build anyway.
Maybe just remember you should get further with Sugar than Spice with folks who are just trying to pay the bills like you are.