I hear you breh.
I'm not sure how many fights you have been in, for all I know you might have been in 10x as many as I have. But, growing up, I was constantly fighting. Every single day almost. No one liked me, I didn't like them.
But moreso to the point, 99% of the time, you are not going to be fighting a professional boxer.
This is how most of the fights went down.
"You really going to use your legs? No legs, fight like a man!"
"You cant just grab him! No grabs, fight like a man!"
"Let him get up, dont hit him when he's down! Fight like a man!"
What do all these sound like? Boxing rules. Boxing was arguably the biggest sport in the world at the time and it shaped how we all viewed manliness and streetfighting.
So, while I agree that a trained boxer can wash most people in a fight without resorting to grabs or legs, the fact is that most people are not trained fighters.
We just adopted boxing for streetfight rules because we saw it as manly and apropos for contest between 2 men.
Fastforward to 2018, if someone gets in a fight with me now and they want to only use boxing techniques on me, I can almost guarantee you that unless they are a real boxer... i'm going to beat the shyt out of them.
And not because i'm better, but because of the inherent restrictions in their martial art of choice