I have no frickin' clue. I just see those ads on cable way too often and hanging out at like drug stores, WalMart and Bed Bath & Beyond.
I'm going to go with shaving emergency though and probably for travel purposes because otherwise why bother to pretend it's just another lipstick? If you need to whip out the heavy artillery for facial fuzz, chances are you've already given someone stubble burn and there's no point in hiding it.