#2 - I waited tables, and a very good waiter once told me that he gives every table the same service whether they do or don't tip, and no matter how much they tip. I feel many servers lack this mentality; which leads to more people tipping less. When I waited tables, 10% was an okay tip, 15% was stellar. Now it seems like 20% is assumed and folks have a social signalling competition to tip 25-30%. Doesn't make sense.
Likewise there is an expectation of good service from waitstaff, but they're not obligated to give good service. They too have the option of giving better or worse service at their discretion. So if a server wants to give everyone equal service that's their right. But if I want to develop a reputation as a good tipper to get my service prioritized over GP by servers who differentiate then that's ok too, and rational I think.