Your idea of "doing there required job" is all wrong, Im very sorry to say. In the field you describe, the idea of tips is to not "do there job" but to add to it as to make the person you are working with feel happy and pleased with there visit. This is why I find it very hard to believe you were a manager, or waitress at all. I have a friend who went up the ranks as you claim you did, and he became district manager. The only thing he asked of the wait staff (beyond normal tasks) was to act happy even if they were not. You see (this is the part your missing) if a person is happy or pleased with a place, they come back, and tell others to come back. If a waiter is mad, boring, monotone or anything of that sort, it doesnt make you feel good, and you will not likely be coming back.
Oh, and if you tip low, or not at all, then you better not come back to the same place offen, esp where I live in NY.
Watch the movie "waiting" and youll see what I mean.
I am not missing anything. Certainly a person's attitude while doing their job is very important, especially when working with the general public. The ambiance they help create will set the tone for the dining experience. I get it.
What I think you are missing is that patrons are not obligated to tip. Leaving a tip, and how much you choose to leave, is entirely voluntary. As I have seen many, many references over the years to exceptional or "above and beyond" service I wanted to get an understanding for exactly what that means to the people who have experienced it. What I am suggesting is that people have become used to indifferent service, and have become used to tipping 15-20% for it. Then when someone gives attentive service they consider it to be exceptional. I disagree, and say that attentive service should be the minimum we expect.
I still think it is ridiculous that the waiter who brings a plate of salad gets tipped $4 less than the waiter who brought out a plate with steak on it. They've done the same job. Provided the same service. However, that is the way the tipping system currently works so there you go.