Focus lighting instruments by hand. Choose templates and gels. With the soaring popularity of moving LED units, the only thing that tomorrow’s stagehands will need to know how to do is tighten the C-clamps and hook up the DMX cables 
But on a slightly more general note: basic navigation.
Why? Will boxes of matches be never-ending in the future, or fish self-cleaning?
A lot of people use small “jet” cigar lighters to light campfires. I did the last time I needed to. On a semi-related note, where can you buy strike anywhere matches?
Comparing small pox vaccine scars.
Using a can opener.
Either the supermarket or a hardware store, although I’m afraid the ones I shop at are a bit far from you.
No, but that sort of thing is becoming a lost art. How many kids today spend much time hunting, fishing, or camping anymore? And the ones that do will go in RVs the size of a Greyhound bus, with electricity, internet, microwaves, and satellite TV.
I’m in my mid 20’s, and half of the things people have listed I didn’t need growing up.
Don’t forget the lost art of adding aluminum foil and adjusting it just right. Or even better standing there “just right” holding the ears with your hand, making yourself a human antenna so your dad can see the important football game with a minimum of snow 
Me, for two. Strike anywhere matches are usually available at the grocery store, or at Walmart.
Especially cursive, as I believe we’ve discussed on the Dope before. I learned it only because my elementary school teachers insisted on teaching it, and the only times I’ve ever used it were on the SAT and LSAT, when I had to copy some absurd phrase out in cursive indicating I understood the ethics rules. Oh, and my signature, of course - though that’s so far from legible it shouldn’t really count.
I handwrite and post several letters a year. usually internationally at that. STAMPS!
I was thinking about that. And “fixing” the reception by hitting the TV on the side. Why did ever think that that would work?
Because with old sets with tubes, dozens of contacts in the tuner, and yards and yards of hand-wired connections, a good thwack often did set things right for a while.
In today’s TVs, the only physical contacts in the set are probably where the HDMI cable plugs in.
Knowing how to fill out a check.
Using a crayon to allow you to record over a commercial cassette tape. There was a hole near the top corner of the tape and you could smash a crayon into it (to fill it w/ the wax) and you’d then be able to record over that Slippery When Wet tape that seemed like a good purchase at the time (and make no mistake, it *was *a good purchase.)
A crayon, really? I just used scotch tape.
A small piece of scotch tape worked perfectly for that, and was more accessible and less messy than smashing a crayon into it. But I concur with the main point.
Manners.
Use a bulb from a flash cube and a scavenged magneto to improvise a detonator.
Churning butter.
Cranking a Model T.