It's only "shocking" if you believe that limiting the population to what you are only able to produce is some sort of law of nature.
Otherwise it's just common sense.
No one - I repeat no one - in the UK is in any way remotely self sufficient. To quote one of the most heavy fact/fun documentary series in human history:
"When was the last time you make something from scratch - including the tools to do it ?"
My DF was a dab hand at making very niche tools (I mean who knew that lifting the shims out of the cam bucket on a Lampredi DOHC was specialist ?). But even he would draw the line at mining the ore and coal to smelt it before making the steel needed.