There's a big difference between formal and informal eating in my school. When I want to eat like a slob and forgo proper table manners I take my tray to a different room to eat (we can eat in any room in the campus center but there is a main hall for eating). This is especially true for chicken which I don't like to cut with a knife but rather to eat with my fingers. I'll be proper in front of guests and strangers but I eat like a pig when nobody is around.
This brings up another thought, when you have a can of soda at supper do you pour it into a glass or drink out of the can? I drink out of the can, who wants to dirty another dish when you are in a family of six and have no dishwasher. My grandparents drink out of a glass. At school we pour it in glasses. I never add ice either, especially with fountain soda, its already cold and ice just waters it down.