I'm not sure why you guys have such a hard time figuring out that a stirrer for coffee should have a little extra surface area to move the coffee around.
People used anything they can get their mitts on as coke spoons this isn't unique to McDonald's but it HAS happened a fee times to several of thier disposable wares.
I know what people used it for but it doesn't negate the fact that it's design just so happened to be useful for that, not that it was designed that way on purpose.
All I've ever seen are those little tiny straws they call swizzle sticks. I would use them like straws when I was a kid. Super small, super hard to suck through straws.