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Starting fire with just a couple sticks.

Chicken doesn't need to be covered in vegetable oil to be cooked.

I guess basic home renovation suff. I literally do these kinds of things for a living. In my experience, it’s not so much that people don’t know how to do this stuff - it’s more that they lack the tools, the time, or they’d just rather pay someone to do it properly. I’ve had jobs where it took me only a minute to fix something they could’ve easily done themselves, but honestly, I can’t blame people for not wanting to mess with something they’re unfamiliar with. Most of the time, I’m not any wiser than they are at the start either - but I guess I just have the ability to figure things out on the fly.

Same as most kids don't know. there are a number of things. Money, listening, how/who to gather information from. I'm missing your point when you put adults in your question.

How to get to the bottom of a conflict without settling on popular opinion.

Mental arithmetic

How to build a house.

90% of the work of building a house can be done by a semi-competent DIY'er. Learning the basics of framing, roofing, plumbing, electrical, drywall, etc, is not that hard.