It's interesting how it's counterintuitive I the exact same way as rubbing dry sand on your weet sand covered feet on the beach takes the sand off. Same mechanism too. Redistribution of the moisture back into the aggregate whole.

At first this feels like a burn, then like someone's putting needles into your hands, and then they just go numb. You can't do precise actions with your hand anymore and soon you'll lose most of the ability to move it at all. You might even lose the body part. All while the core of your body is still warm and you're still able to walk and talk.

But as said, not everyone experiences this. For some people, when they get cold, their body increases circulation in the hands, keeping them warm enough to continue working no matter what.

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1. In extreme cases, this is called white hands syndrome or reynauds syndrome and primarily affects women. It seems to have a hereditary component, but worsens permanently whenever the hands experience cold or vibration.

Returning circulation is much more brutal than it might sound.

A lot of things come from somewhere and are not arbitrary. That’s all that’s being asked here.

Or maybe people understood initially that you should do the rubbing next to a fire. And then the rubbing only has positive efect because it lets the person administering it feel when the heat is too much, and naturally adjusts the distance to prevent burns or injury from too fast warming up.

Or maybe someone told people to do it because they thought it might help and never bothered to check if it does anything or not.

Or maybe people did know it does nothing but there was no other option and doing something about the injury felt better than doing nothing.

Maybe it was doing mechanically nothing but the care and personal touch had a beneficial effect due to placebo.

Maybe it made the injury worse, thus more likely that they amputated and paradoxically that saved the injured from worse outcomes like gangrene.

There is so many other possibility than “if they did it it must have worked”. Who knows.

Bloodletting is standard of care for hemochromotosis; you can use leeches for that, but just drawing blood is probably more efficient; some blood banks will let you donate it, some say no because the donation isn't supposed to be of benefit to the donor.

Certainly, a lot of conditions where bloodletting was used don't warrant it, but it's not altogther bad.

I don't think there's a good use case for a lobotomy, though.