And of the few situations where they do do it, you would be very very unluckly to actually be denied boarding, even at that you'll be put on another flight on the exact same route on the same day. Hardly that unreasonable in the overall scheme of things, and certainly not something I'd be getting too worked up about!
Presumably you apply the same standards to other situations. You get much sought after tickets to a Madonna concert, when you get there you find that your seats have been sold twice, and sadly, normally 10% of people who book concert tickets don't turn up, but on this occassion that didn't happen. So here is a refund of the ticket price. I am quite impressed that you would shrug your shoulders and say oh well, hardly anything to get worked up about is it. C'est la vie. Bollocks.