Why's boxing, MMA, and wrestling matched by weight class?

Who wants to see:

1. David vs. Goliath match
2. Goliath vs. Goliath match
3. David vs. David match.

Isn't #1 what we all wanna see? Of course, David might get killed. That's the whole exciting point! And if he somehow beats Goliath, that would be so epic.

I don't understand why we stopped doing this stuff. Safety stuff, I figure. There was some soccer mom that wanted to take over it. But it was way better before. Also in sumo:

50kg weight diff, no problem. Let's see what happens. Real-life is this way. Nobody weight matches soldiers against teach other. If you're a 100kg soldier, you gotta defeat the 150kg soldier. He's not gonna be like, "Oh, you're outside of my weight class."

Updates
1 y
It's not even about fighting that much anymore. It's like who can cut weight drinking nothing but water for 5 days while sweating it off for their weigh-in. Then regain it all and be 10lbs heavier in the ring. Get rid of this weight class stuff. That shit kills people.
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1 y
This is dumb as shit. And it has nothing to do with combat.
https://youtu.be/klFeEHpYfqY
Why's boxing, MMA, and wrestling matched by weight class?
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