At the UCs and *A lounges I visit, they all have bussing staff who are supposed to keep the place clean and to clear away used dishes etc. However, I take it as my responsibility to leave the area I'm vacating reasonably tidy. To do that, I put items like banana skins and food wrappers on the plate. If I have personal trash, I put it in an available trash can - but I'm not going to put their crockery plates in a trash can!