Everyone should work some form of retail job at least once in their life.
I was a motorcycle mechanic for six years before going to college. Some customers where a joy, you looked forward to seeing them, most were just average Joes that needed work done, and a very small few were arrogant self entitled jerks, but it was a job, and you had to deal with it.
Some of the nicest people I know have had retail experience in their life.
I've heard the comment multiple times that everyone should work in a restaurant at least once in their lives so they have a better understanding of what the employees go through. I tend to agree, and I would probably add retail in there as well.