Skill Testing Question

A Wired article today reminded me of something that has always bothered me:  why do contests have skill testing questions?  Apparently there is a law that requires companies to have a way for people to enter for free, so they always have had a test of some sort for the winner.  That way the game isn’t completely left to chance, but requires skill instead.  Ya right.  It’s not the case in the US, by the way, where you aren’t obliged to do anything to get your prize.
Weird.  But now I know.