Don't use it, lose it

People think that the easy dissemination of information makes it difficult to lose knowledge in the modern age.

Actually, it's extremely easy to to lose knowledge. Especially technical expertise. So much of it is very specialized and only existent in the private hands of corporations. And within these corporations, specific and important facts are only kept in the minds of a handful of people.

If the engineers depart and the line workers depart, without replacement, you've already lost most of the knowledge.

For instance, the principals of an internal combustion engine are well known, and there's quite a bit more than that circulating around in papers. Do you think that's enough to reconstruct a modern car engine? Engine fundamentals from the Model T to the Fiesta haven't changed. But over the last century, Ford has figured out how to squeeze out more than 3 times the mileage and 6 times the power with an engine volume of half the size. Do you know what they did? Do you think your educational institution knows what they did? Not a chance, unless your professor worked in a very specific field within the industry. Even then, his knowledge grows more outdated year by year as Ford engineers continue to squeeze out a few more percentage points of performance year by year.

Or let's say that you already know that you can get a 5% efficiency gain by tweaking the inlet aero. How would you know where to tweak? You'd have to go through all the testing that was done before, and you'd need to design and build the infrastructure to conduct the tests in the first place.

It's the same across all fields, from cars to bridges to computers. Good luck building a modern virtual machine using the Dragon Book. And that's still only talking design knowledge.

Im CAD hat's passt.

It fits in CAD. Not good enough.

You can't learn how to build something without actually building it and, more than anything else, this is something kept exclusively in the minds of workers. And god help you if the toolset had been struck already (which is common), because now all of sudden all of your work instructions are worthless without the accompanying equipment. Now you have to redesign and rebuild the infrastructure too and go through the teething process all over again. Think you can make a violin from an instruction book? Nope, you learn by building a violin and a lot of crappy violins.

See how we've decided to stop going to the moon for a couple of decades and suddenly it's a pain in the ass to figure out how to do it again. And that's with all of the previous generation's artifacts around, more computing power than our predecessors could ever imagine and an extremely competent corp of people who've been shooting things into space non-stop in the intermediate period. Sure you don't have to go though the paradigm shift breakthroughs again, but most of being able to do something is just grinding, and that's a feat that'll need to be replicated if you ever forget. Technology has not dark age proofed us.