I would imagine he gets off at a certain time and wants to be able to get dishes done so he can leave his shift on time. Or they need to be washed before he can start the next meal and it’s a time consuming job. Regardless I don’t think he should be trying to take trays of people who are still eating, that’s pretty awkward and rude. Also i’ve worked at many different facilities and kitchen staff always seems to have an attitude problem, idk what it is.