If I'm paying working wages for an hour at a table, I expect to have a worker sitting next to my table the whole time.
My waitress is sometimes not available to fill my drink instantly because she has many tables. As such, I'm not expected to pay her full pay. Solid service usually gets about 15%. I've gone substantially higher if I really like the person but I'm not gonna go overboard out of some debt I feel to them. If their job is ****ty, they should take that up with whoever forced them to work there.