It happens in rare occasions in real life. But very rarely, and people never walk away from it. To pick one sample, with medical teams on hand, not a single person out of some 200 survived a jump from the WTC. The complaint is generally that a high-level fighter can jump from a building and suffer zero risk that they won't be able to walk away from it.
Nope. Oh, certainly, it's rare, but people do walk away from it. Yes, it's the extraordinary for it to happen, but adventurers are extraordinary people.
All the mythological characters have explanations; Hercules was the son of Zeus, Achilles was dipped by the heel, Perseus was not only the son of a god, he always had tailored magical items given to him by the gods. Why is it so hard to ask for some explanation why a mortal can suddenly after a few levels survive a 100 ft fall?
What about Sir Roland? Beowulf?
Everyone involved in the Three Kingdoms?
There isn't a problem here that you're seeing.
The difference is the source of heroism. Previously, it was generally accepted that the gods ruled all. The supernatural and the natural had a clear separation, which is why in
so many ancient religions, visions and possession was such a big deal - it allowed the mortal man to understand the supernatural. Mankind did not control his own destiny. Therefore, heroes had to be related to divinity - it's what allowed them to alter the world.
As time went on, the idea of self determinism grew far more popular, and romanticism of a "past age of magic" grew. So you had modern pulp characters who could do the impossible but had their powers from some mystical rite they underwent, or from ancient practices they followed.
Later, self determinism reached full popularity and the elements of the supernatural were more frowned on. You had characters who represented The Best Detective, The Toughest Cop, and other similar archtypes. These are characters who
still did the extraordinary, but they did it because of extreme training, or from esoteric understanding of science and natural laws. Batman is a normal man who, even without his gadgets, can do the extraordinary. James Bond has a vague supernatural luck that allows him to do things no other man can.
So, the heroism hasn't changed, but their
roots have.
And really, how are wizards exempt from this? Name a normal, mortal human wizard that wasn't D&D related. Name one. Merlin was of supernatural heritage, Gandalf was an angel, and the original wise bearded wizard was the god Odin. None of those are normal human beings who just took on apprenticehood at ye old local wizard tower. That is what is perhaps the most darkly humorous part of this entire argument - a mortal warrior who does the extraordinary is
entirely in line with medieval fantasy, but a mortal wizard? That's a D&D-ism only.