Why use the seats on the bus when there's a whole floor?

You know those seats on the bus, that you fold down to sit on, and that goes up again when you leave your seat.

Sat on one of those today, on my way home from a friends place. Got up quickly to throw a paper in the bin just a meter away, in front of me.

Then, forgot what kind of seat it was, and sat down without looking. Of course the seat had gone up as soon as I got up, so when I sat down again I ended up on the floor instead of the seat.

Just a bit embarassing.