You are right, there is no reason they "cannot" have the necessary skills. Many do. Just pointing out that the majority, "I think" do not. I could be totally wrong though. But if we suddenly found ourselves back in the stone ages tomorrow, I would think the odds of survival would be far greater with those in skilled trade professions such as mechanics, carpenters, etc as opposed to those BS degree in arts and crafts.
A wee bitty unfair "I think". Most of the PhDs I have known have also been very practical people, and not head in the clouds academics.
I think we all consider the back to the stone age scenario from time to time (there was a long and informative thread on here about it a couple of years or so ago) and my team includes only one PhD (my son) but also a highly qualified chemist, his vet wife and my son's medical doctor wife. There are others, particularly a whizz with electronics, mechanics and a sound grasp of alternative small scale energy uses.
Living where I do there is an abundance of practical peasants - I use the word with respect. I consider myself a peasant too. These people already appear to provide most of their requirements from their small plots of land by the use of hand labour or very small machines. How many of you regularly see folks doing their laundry in the river; clean the tripes and guts of slaughtered animals likewise - the river is called the Tripeiro, or in recent years have seen a family threshing their grain crop with a flail? They will survive no matter what. Bread, wine, olive oil, vegetables, milk, cheese and meat are all mankind needs.
There is a shortage of the skills the rest of us possess and bartering will occur.