I agree that these mandatory tips are highly annoying.

I was once out on a business lunch with about 13 others. When it was noticed that there was a mandatory tip of 15% for a party of our size, I called the waitress over and explained to her (politely) that we finds the idea of a mandatory tip insulting.

She listened politely and promised to let the cashier know. The lunch was fine and when the check came, it did NOT include the mandatory tip.

The upshot was that she received a 20% tip, and the customer was happy. But you can be sure ONLY the absolute minimum would have been tipped had it been automatic.

Mandatory tipping is just an obnoxious practice, and I definitely make it my policy to NEVER give extra tip any time anybody tries to charge me a mandatory tip.