Not ashamed at all. If my food is brought out cold or drinks watered down, a complaint to the management is immediately in order.
It doesn't cause me the least bit of chagrin. It is a not a moral problem either for me. From my place of birth and residence of most of my childhood and early adult life, tipping was unheard of.
Those waitstaff that do not report their full tip income to the IRS feel no shame in cheating the us government.