The Customer is Usually a Douche
Maybe I'm being unfair...
Still, it isn't so hard to understand how to bus your own trays, is it? Every day without fail, I find bus-bins filled with trash despite the fact that the trash can is literally next to the bus-bin. AND it's labeled 'trash', and separately beside it, 'trays'. There does seem to be a generational divide. Younger customers seem to grasp the concept of scraping your tray off into the trash, then placing it in/beside the bus-bin. Older customers seem to get confused, exasperated, and then dump everything into the bin without thinking about it. Here's something they probably don't know: it's my job to clean the bus-bins if they get disgusting.
This is why I try to take people's trays before they have a chance to do it themselves. Which brings me to my next annoyance: the customer who refuses to let you take away dirty trays/dishes despite the fact that they're done eating. I have no clue why they take a protective attitude over their used dishes and cutlery. The best part about those customers is that when they decide it's time to go, they leave their tray/dishes/cutlery right on the table.