>I can trivially judge the necessity of service but unless I am an expert in the domain I cannot judge the quality of service and very often the entire point of the service is to outsource expertise.
The entire point of this service is to improve your subjective experience - if you can't evaluate that then you probably need a legal guardian.
I can judge whether I had a good time, but is it the waiter's time things took long or was somebody in the kitchen slow or some other customer holding them up? Is the stain on the table the fault from the waiter not replacing everything or the boss's policy? etc. And if the food and my company is great even the worst waiter has little impact in that.
The waiter is the face of the establishment, but there are many things out of the control of even the best server.
They can do as much as they want. It's the owner's responsibility, thought. The owner makes the decisions. The waiter is the underpaid person, which will be replaced if they complain too much.
If I don't like a place I let the owner know and reduce my spending. If I like the place I tell the owner and spend more.
The entire point of this service is to improve your subjective experience - if you can't evaluate that then you probably need a legal guardian.