Champion Mastery point system

Why does the system give so much exp. from simply winning a game instead of how well you do? Wouldn't it be more reasonable to gain exp. based on your performance and have a small bonus for the win, for example getting 1+k exp from a game where you feed 3-18 and winning the game, compared to getting 200 exp for going 18-3 and losing the game, it doesn't seem fair to the person carrying the game while the person having a bad game gets more heavily rewarded. Not many people care much for champion mastery points but its a fun incentive for my friends and I. it would be good to have a response to why the system is this way, and I would love to talk more about why it should be changed, maybe it could even improve the system as a whole. -Xipae