The whole idea of a tip being 10-15% of the total bill doesn’t seem
quite right to me. Take two equally proficient waiter/waitresses, one
working at an expensive restaurant, the other working at a neighbor
bar or café. I’ll go 15% at an expensive restaurant, but I might pay 30%
at a bar or café. People who provide good service shouldn’t be penalized
because of the price of food or wine in the establishment where they work.

Just my opinion,
Dick