Gain/Lose LP based on how you played instead of Winning/Losing a game

Riot why does Gaining or Losing LP have to be based off winning or losing a ranked game. Why can't it be based on the individuals performance. I just got done with one of my series games, which i lost because of a pair of players that turned the whole team against me for calling shots. Just because the malphite was fed, even though he kept suicide into the enemy team and feeding them. They made so many calls that cost us a game, baron which i tried to ping them of so many times, elder as well. This malphite had my team eating out of his hands even though i solo carried my adc as support through the bot lane. No matter how many bad calls this malphite made, example: telling our sivir to go face check the elder dragon pit solo, cause i died saving my teams *** so i could not face check instead of her. My team ended up clearning out mid bot, all the way to nexus, and this malphite and orianna decided to push top instead of going in even though we had the superior team fight. Every single fight we won, is they didnt engage while everyone else was to far away clearing crashing waves or finishing our items. They just kept dragging out the game instead of ending then 1 baron call, while their whole team was up, even though I tried to ping them off, i was even zoning the enemy team the best i could they would not break off baron and we lost the fight because i died then they did. So again i must ask why do we have to lose LP because of trolls like these? Ive lost a hand full of games just like this. I made alot of great calls earlier in the game, dragons towers, setting up ganks and roaming to get mid ahead, and the second malphite got kills shot calling was taken away and the team was even trash talking me when i tried to call shots. Its really frustrating losing games because of this. So riot can you please do something about this? Cause its really flipping annoying. Especially when its a damn series game.