The ground pin, when "up", is higher than the hot, so in certain situations it can prevent something from shorting the hot and neutral. Code (?) or convention requires it if you have a metal faceplate, and hospitals require it. People generally like them mounted ground down because then they look like little faces. :-)
alt Hacker News
The ground pin, when "up", is higher than the hot, so in certain situations it can prevent something from shorting the hot and neutral. Code (?) or convention requires it if you have a metal faceplate, and hospitals require it. People generally like them mounted ground down because then they look like little faces. :-)
edit: Not code, just convention.