I think the obsession with KO head strikes = real fight is because we are grapplers talking among ourselves. That's the thing we don't do so it seems scarier. And there's an inferiority complex about it.
Regular people look at things exactly the opposite. Say you get in a bar fight and put a guy unconscious. Cops show up. If the witnesses say you threw a punch and knocked him out, that's probably simple assault. If the witnesses say you threw him down, got on top of him, and choked him unconscious, that's probably aggravated if not attempted murder. Regular people view chokes as damn near lethal force. So it's exactly the opposite of our view in the real world.
Of course that is untrained ignorance. But our joint locks are definitely serious force. And that's what we are doing in competition.
I'm not sure why hurting people is not considered part of BJJ competition. That is the goal of a submission. Sure they might tap in time. They also might not, and I see guys getting injured this way every single tournament I go to. It's pretty common to watch a guy limp off the mat, rubbing whatever got caught. Tough to go tell those guys that their injuries aren't real because a BJJ match is not a real fight.
I don't think viewing brutal KO as the goal of boxing is accurate either. That is just one possible strategy, and really it's not even the most common one. Explosive power puncher makes exciting fights on PPV, but overall it's a pretty rare trait in a guy. It gets even rarer at the lighter weights. Most new guys come in wanting to be power punchers and most coaches laugh and try to steer them away from that style.
Plenty of guys try to win with a classic boxing strategy of stick and move, combinations, and just wearing the guy down round after round. The KO comes not as some brutal lights out hit but a TKO from three knockdown, the ref stopping it, body shot, the guy just refusing to get up, etc. Or you go the distance and win the decision. This is especially common in amateur boxing where the scoring is literally point fighting same as TKD. There is no bonus for damage.
There are levels to all these things, and it's just weird to assume that striking is so much more hardcore every time. I agree that two 40 year old white belts rolling at a local tournament is nowhere near the same level as getting KOed by prime Tyson. That being said, two 40 year old investment bankers boxing an amateur match for charity is nowhere near the same level as getting your knee ripped up by Palhares at ADCC.