Not on an individual scale, no, but when you consider the millions of visits and views they get per year it adds up from a global / zoomed out point of view.
I'm sure with some math you can make a calculation on how much bandwidth and energy was saved with this One Clever Trick.
A government is the perfect place to look at this "zoomed out" view.
Your citizens an average rate of pay of Y per year. Some of time they save by getting stuff done on a government website will be put into getting more economic work done. If the citizens do 10 billion pageviews of gov.uk per year, and you shave off 20ms, thats 27 human-years of work per year. So it is certainly worth making this optimization, even if it takes a few people a few months to figure out how to remove jquery.
I'm sure with some math you can make a calculation on how much bandwidth and energy was saved with this One Clever Trick.