I met a kid who didn't understand the concept of washing dishes.
Wife went back to college. New city, didn't know anyone. Started a Movie Night thing to meet some people and build a social circle.
We provided a home cooked meal, a fun movies that most people hadn't seen, and a place to gather - went over great and had 6-12 people showing up each week to hang out and talk and eat our food. Generally good people, because she was going back to college - a lot of college kids came. All good.
I knew this one guy was from a rich family, his first night there he's bragging to everyone who'll listen about this 30k+ truck his parents just bought him and telling everybody how awesome he is.
After everything is done we're collecting dishes in the kitchen and he walks over and following me to the kitchen he walks in and puts his dish and silverware in the trash can.
"Hey man, what are you doing?" I'm assuming he brain blanked for a second, no big deal.
"What?"
"Give me the dishes, don't throw em out." It's a ceramic plate, not a paper one...
"Why?" He asks, obviously confused.
"... I'm going to wash it."
"Why?" He repeats.
...Now I'm confused. "So it'll be clean for next time?"
"Oh! Like the dining hall. Oh. Ok. Sure."
I find out later he basically lives off take out, restaurants, etc - he's never cooked anything in his life, his family has servants who clean up after meals and .... and he just assumed dishes were something you threw out when you were done. College was the first place where he even saw the idea of putting dishes somewhere other than the trash (or leaving them on the table) afterward.
He wasn't a bad guy honestly, just... I was amazed something so incredibly basic had slipped by him for years.