I'm afraid you believe wrong!
I don't believe I do! What I'm saying is a very very small number of flights in proportion to the overall total are ever actually overbooked, whether the capability to do so is there or otherwise.
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.
You would presume wrong unless we're talking specifically Madonna tickets in which case you would be right. Besides seats aren't over sold at concerts because they can't offer you a seat at another concert at the same venue by the same artist later that day. If they could, they probably would and it would be quite logical to do so.
Anyway the main point I suppose I'm making overall is that a chronic problem of overselling seats at Ryanair does not exist and you'd be very very unlucky to ever fall victim to it. Then even if you are that poor unfortunate sod, you'll still be travelling at some point that day, you'll never be left stranded at some remote airport overnight or anything. So sorry but I still won't be getting worked up about it anytime soon.