I'll do my best:
Yes, walking around slippers are furry, with not so much grip on the bottom, and the bathrooms are wet rooms. So, I'd either fall over, or leave wet marks on the floor in the rest of the flat.
We have quite a lot of guests, mainly friends who are to drunk to find their way home, but also visiting friends and family, none of whom tend to bring their own.
I don't consider my feet to be particularly sweaty (more than any of the rest of me, anyway), but I wear flip flops most of the time outside, and the streets can be pretty filthy, so bare feet on the tiled floors tend to leave a lot of marks. Combine this with the first point: dirty feet + wet room + walking back through the flat. Domestic waiting to happen.
That said, I did exactly that about 10 minutes ago, and cleaned up before she noticed
As I said, I find they don't really fit, so I just go with bare feet and...tread lightly (sorry)
I hope that helps.