I don't know if I should tip at a Dim Sum place in the US where the service is from carts.

There is no one who can be specifically identified as my waiter since we are grabbing stuff off many different carts pushed by many different folks as well as having tea brought by someone else.

I was told by one Chinese lady that her brother had worked in a Dim Sum place in Chicago years ago where the workers were given work clothes with no pockets so they could not keep the tips, all of which were confiscated by the owners.

And, I have asked several customers at various dim sum places what they do and gotten contradictory answers.

So, what do knowledgeable flyer talkers do? And why?