Just like internet discourse would improve if people refrained from typing what they wouldn't say to someone's face, these tipping issues would be practically nonexistent if the owners tried to force workers to verbally request a tip after handing over a muffin.

To me, these tip requests deserve as much respect as the old inner city window washer routines[1]. They are insulting and show a complete lack of respect for the customer who chose your shop to spend their time and money.

[1] Edit: or any aggressive panhandling.