On the other end of the spectrum: there is a burger joint back home that will put a pickle on the sandwiches even if you ask them not to (and remind them and their manager and it ends up on the ticket in front of the cook/preparer). In this case (at least for me), free pickles equals worse customer service.
The real point was "if you're generous, you'll win loyal customers."
Both points are valid. Give your customers what they want and be nice (even generous) while you do it.