Because I personally do not know it does not mean it's lost! (I don't
know how to extract nickel from ore, either, but has _that_ knowledge
been lost? Hardly!) Of course, it doesn't mean it hasn't, either....
Exactly just because you "know" how to do something doesn't mean you can
do it. I know how to make a statue or a nice dining room table but I
lack the finer skill to actually do it. That's where the skills are
being lost, these things take practise.
Dan