Why is shame such a fundamental concept in the American restaurant system?

“Yeah the food you bought cost $20 but if you don’t give us $25 you’re a POS”

“Yeah we close at 11 pm but if you’re here after 10:30 pm you’re a POS”

How does such a large industry manage to have so many unspoken rules? Why can’t restaurants just increase prices by 15-20% and declare that tips are genuinely optional and only for truly exceptional service? Why can’t managers/owners change their hours to be something like “no tables will be sat after 10 pm, no food can be ordered after 10:30 pm, and you must leave the building by 11 pm” and then communicate to their workers that the closing shift will probably end around 11:30 pm? And most importantly, in my mind at least, why has the cultural discourse around this decided that all this is the customer’s fault rather than the managers/owners?