Thing is some people never were good at reading/using maps, much less creating them. Even with GPS at hand I still prefer seeing a map to know where I'm going. Anyway, retaining at least a modicum of "classic" skills is beneficial. After all, GPS isn't infallible. As with all complex technologies, possibility of failure warrants having alternatives.
I was recently on a cruise, someone asked the ship's navigator whether officers were trained on using old instruments like the sextant. He replied that they were, and continue to drill on their use. Sure, the ship has up-to-date equipment, but knowing the "old ways" is potentially still relevant.
> "The question is: what are the second- and third-order effects of losing those skills, or not learning them in the first place?"
Naturally, old skills fade with advent of newer methods. There's a shortage of ferriers, people who shoe horses. Very few people are being apprenticed in the trade. (Though I'm told the work pays very well.) Owning horses is a niche but robust interest, so ferriers have full workloads, the occupation is not disappearing.
Point is that in real-world terms losing skills diminishes the richness of human lives because there's value in all constructive human endeavor. Similarly an individual's life is enriched by acquiring fundamental skills even if seldom used. Of course we have to parcel our time wisely, but sparing a bit of time to exercise basic capabilities is probably a good idea.