Tipping seems to become a norm, everywhere in the US
I've started paying attention to what the people in line in front of me select for a tip. At a location I visit frequently, they have ready-made sandwiches, a few coolers with bulk-made salads, drinks, etc. They also make espresso drinks and serve ice cream. I am both amazed and dismayed that people will grab a salad and a drink from the cooler, and when they're rung up, they'll tip 15%. I always want to ask, "What are you tipping for? What service did you receive?" But the social contract says that you don't butt into other people's business. It seems that here in the US, we have normalized tipping workers even when they offer no service at all other than running a register.