Seeing the other responses I bet (tongue slightly in cheek) that the
reason is some junior electrian mounted them all wrong in a new house
and when the boss noticed he came up with the "so something doesn't fall
on it" excuse so that they wouldn't have to re-do all the outlets. Word
spread of this new, "safer" way to install the outlets and now people
actually ask for it despite the fact that it screws up a lot of things
that you try to plug in that assume the grounding pin is on the bottom.
