>>Maybe because the one pair of pants covers two legs? But then a long-sleeved shirt (that covers two arms) would be a "pair of shirts". Too much thinking on a muggy Saturday afternoon. ;)
>
>I might use a single sock, for example, if my other foot is in a cast.

Or if you're visiting a bank with an offer they can't refuse :).

>But I find it a little more unlikely to use a single "pant"!

People usually pant in pairs ;).

{nb. It's Saturday, and I was working on the bathroom flooring all day. Take this as relaxation of a rested mind and weary body.}