Why doesn't Riot want performance-based LP?

Let me get it clear - this ISN'T a criticism, i'm generally inexperienced in game design and want to ask a genuine question to improve my knowledge.

For example, i know wild rift and valorant have some systems placed that measures your performance to decide whether you should lose or gain less LP based on how you did.

I haven't played ranked for long, but since i started i thought it was pretty weird that someone who might go 0/20/1 loses/gains the same amount of LP that someone who went 20/0/10 does.

Of course i heard a good argument for it, that goes something like "KDA doesnt tell the whole story"... well league games already track a lot of things that could also be used to evaluate performance - like champion damage, vision score, objectives, turret damage, CS and ally healing and shielding -- the things that would be most difficult to track are be map pressure, space creation and other macro decisions.

Still, is that the only argument for it? I'm intrested to hear everyones thoughts. Thank you!