I've delivered a Sonic Air package, which I thought was odd. Was a few years ago, and for some reason we had it. Had sonic air labels on it, but then had one of our labels on it as well. Think because it came in, in time for us to deliver, was put on my truck (came in from airport to us). Only seen it that one time though.
Oh, and onto why? Well, some people need parts for a machine that have to be there asap. Hours can be a big thing. Had a company that had a part overnighted from Germany. Weighed 68#'s, so you know it cost some coin (this was pre over 70's). If they would've had sonic air at the time, I bet they'd have used it too. But was a part for a machine and every hour it was down was costing them like $10,000. So paying that price wasn't a problem at all.