I rarely eat out these days (sheer luxury!) but I have seen how obnoxious some customers can be. Is it a class thing, regarding the staff who serve them literally like servants?
I make a point of being friendly to supermarket staff, I know they get quite a lot of abuse too. What is wrong with people??
In the Pre-Covid days, supermarket staff were my heroes. I went in almost daily. You build a relationship with some of them.
I remember waiting in the checkout line and my husband and I were harassed by another customer, who took exception to our clothing(which were perhaps a bit unusual, but far from offensive). She yelled for a manager, and one came. She complained to him that we shouldn't be allowed in the store... and he proceeded to escort her out, and said if there was anymore commotion, he'd call the police.
The look on her face was priceless.