LP gain and MMR
So I have been playing Ranked for over a year now and a friend of mine is in the same elo range as I am. Currently I'm in Gold 3 and he is in Gold 4, but I gain less LP per win than him even tho my win rate is higher than his. I currently gain 18/19 LP per win and somehow he gains 27 LP per win so I was wondering if anyone knew why that is. Even when I go on huge winning streaks like 10 or 12 games in a row won with good kda, cs, KP% and vision score my LP gain doesnt increase, it remains at 18/19 LP per win. And even if he goes on a big losing streak his gain remains at 27 LP per win. It's really frustrating and I dont know why the system does this, our MMR should be identical but somehow I'm being screwed out of LP. Even in season 8 before the ranked changes I checked my MMR on op.gg and even when my MMR was 2 devisions(so for example I was G3 at the moment, my MMR would be G1) above my current rank my LP gain wouldn't even increase.
Does anyone know why this is? Please help