when i had housemates we each took responsibility for a public area of the house for cleaning - i had the kitchen and would clean only the kitchen (and my own room) etc.

anyway one of the girls had the bathroom and i kinda went away for a couple months and when i came back i lifted the toilet seat and it was really unpleasantly unclean underneath.

the rest of the bathroom was spotless, fresh and shiny. only the ceramic under the toilet seat was gross.

it occurred to me that the girl had never once lifted a toilet seat in her life. think about that for a few....

i assume her dad was well-trained and always put the seat down