Ditto. Everyone should have to work retail with customers at least once.
It has been almost 50 years since I worked retail in high school, yet I still vividly remember having to smile and take it when a customer was having a bad day and decided to vent on some poor kid working at a customer service desk.
I worked retail/hospitality for more years than I care to remember.
Now, whenever interacting with anyone in Customer Service, I play a game where I try to be the nicest person they'll encounter all day. Be a fountain, not a drain.
Back in my high school and college days, I worked at a Radio Shack, then at Lafayette Electronics (remember them?) and finally at a high end audio shop called Opus 2. Even had occasion to meet Andres Segovia one evening when he came to play for a demo of Audio Research electronics and Magneplanar Tympani 1Ds. But that’s another story.