To Shoe - or not to Shoe

As a sometime bus-driver, myself, I am interested in the differences I see in Korean bus-drivers. This was inspired by seeing one lose his toothbrush yesterday, as we were taking a corner.
I try, always, to avoid generalisations in the sense of assuming all Koreans, say, act in such and such a way - simply because I have seen one person do a particular thing. That said, in class, for instance, it is quite rare for one student to know something that everyone else doesn't know - if one student says he doesn't know where Antarctica is it's a fair bet that no-one else will know, either.
Back to bus-drivers: Often enough they wear slippers in the bus - on the basis, I imagine, that they are at work. Usually they wear white gloves, often they have a roll of toilet paper within handy reach (a bit of a worry, that, at first sight) , and now I've seen one have his toothbrush roll onto the floor.
The slipper-thing is a mystery for me. They are a type of scuff, perhaps, the sort of thing with no toes or back. Your toes hang out the front and your whole foot slips out the back because there's nothing there to keep it in. They're called slippers here, in English.
My problem is knowing when to wear the bloody things. In general, you could say they are worn inside (the house) because people sit and sleep on the floor (and the slippers aren't covered with the sort of thing you step in on the footpath). So far so good. Restaurants are sort of OK, as well, I guess, if they are ones where you have to sit on the floor. Where it gets harder is deciding (knowing) about other buildings. I notice that our spectacle-dispensers wear them at work - should I? Do they sleep/eat on the floor there? Do bus-drivers - should I? At school the students certainly sleep much of the day, but they are sitting in chairs, not on the floor and we all have to wear them. At a place I go to to do classes sometimes neither I nor the students have to wear slippers - but some of the people who work there full-time seem to. Ho hum.