It's their culture. It's well beyond just being a fighter. There's a word they made up, karoshi, which means death by overwork. It's hard to pinpoint exactly where it came from. There's the Confucian influence, which is not taught so overtly but taken from the influence of Chinese culture, and that emphasizes group before self. The Buddhist aspect, especially Zen, which is more hardnosed and tough minded than most other forms of Buddhism. Then combine that with Japan's unique culture-- largely due to being an island nation, it developed differently and was more isolated, so nationalism is a big thing. THEN the industrial revolution and WW2 get mixed in, you have quite the combination. The federal government pushed a nationalist identity HARD to help catch up with the rest of the industrialized world, you then get into how whacky the national religion that believed in the sun goddess Amaterasu, you have a perfect situation for that type of thing to occur. They literally told everyone that everybody in the entire country is a direct descendant of the sun goddess, that they can't be defeated, even to the point that Japanese is a super difficult and complicated language that non Japanese can never really learn (it's not lol) and they BELIEVED it to the extend that they were communicating over unencrypted radio signals in WW2, just giving away plans and positions. VERY arrogant, very racist, very closed minded. So that type of display is seen as really brave, the person that does it will receive accolades, and it will be held over others' heads as a point of shame for not being so selfless as a guy like Tamura that gets crushed by Bob Sapp in five seconds.