Decimalisation - just another thing to attribute our 'fall' to. That and using 's' in all the wrong words.
Aside from odd bits of slang and certain archaic traditions the system has pretty much disappeared. Us post-decimalisation babies are blissfully unaware of the monetary-mathematical struggles of our forebears.
Time to hammer the final nail into pounds and ounces and our decline will be complete.
As a kid I read the Horatio Hornblower books where money was often valued in shillings, guineas, half-crowns, etc. In 1995 or so, I happened to be emailing this English guy I ran across on the Internet who had been born in the late seventies. I asked him to explain the money system (research on the Internet back then wasn't anything like it is today, and I wasn't about to make the effort to look it up in a library), and he said there were only pounds, and 100 pence to the pound. I asked him didn't there used to be lots of other measurements, but he was completely unaware that there had ever been anything else.