Why no Variable LP

I main support and it really gets on my nerves that I can go 1-2-25 and my kill participation was higher then anyone else and I managed to get my adc fed. Then we lose. -15lp or more is the result. This is common for me (the fate of trying to crawl up the ranks as support).

Does this sound familiar? i know all of us have had that game where we are carrying the team only to lose because someone keeps getting caught out, or no one groups, or no one manages wave, or chases a kill for 5 minutes instead of getting that free dragon and tower. This might be a bit more common on supports but I've had an occasion game when I'm mid or top and something similar happens.

That really isn't your fault and sure many of us can always improve our game some more but is there a reason LP loss isn't determined by in game stats like KDA and kill participation? I know it would be two sided and that games I win I would get less LP when I played poorly and got carried but this just seems like a good way to divide out good/poor players. I think that great performance should be rewarded not punished, even if it is only a minor reduction/increase in LP loss/gain.

What is Riot's thoughts on this? What is the community's thoughts on this?