Being able to send a dish back doesn't exist because waiters rely on tips. If restaurant owners and managers didn't accept it, waiters would not be permitted to do it. It's not like waiters take a plate back to the line and beg the cooks to do another one because otherwise they won't get tipped. "The customer is always right" is why American service (in general, not just in restaurants) is customer-friendly. It has nothing to do with tipping waitstaff.