Employees do no more than employees at say, McDonald's. In fact probably less. Push a button, right amount of coffee pours into cup. Move cup. Push button, right amount of milk pours into cup. Move cup.
Replacing people by robots will make no difference to the final product.
What we need to wait and see is whether consumers want to be served by a human or whether they don't care. We'll have an answer very soon because for fast food and coffee shops there's just a couple of years before humans become operationally optional.
Personally, in a high end place where staff adds value I will care, but I couldn't care less in a Costa Coffee or McDonald's.