A lot of it is just cluelessness, like expecting a young mechanic to diagnosis carburetor problems.
Example # 1. I stopped on a ride at a local LBS, because something had come loose that I had just [obviously insufficiently] tightened before leaving. I was on my 3 speed. This is a place stuffed to the rafters with carbon bikes and expensive clothes. The first wrench the young mechanic tried didn't fit. He said "it must be a 14." I replied "No it is probably whitworth, but 11/16th fits." He looked at me like I had just grown horns out of my head. I don't think whitworth was in his vocabulary and I'm not sure he had ever used ASE wrenches on a bicycle
Example
#2 . I stopped at a different LBS, looking for a cheap seat post. This place sells lots of beach cruisers and hybrids. I asked if he had any 1" seat posts. He said no. I turned to leave, but thought to turn back and ask "What about 25.4?" He pulled out a full shoe box and asked "Is that what 25.4 is?" He doesn't get the pass that the kid got. He is at least fifty and has supposedly been in the business for decades.