How come I lose 21 IP when my teamate leaves game or doesn't ever join?

Like its not even just about me. If a guy goes afk on my team or disconnects, when my team inevitably loses we all lose IP. I don't understand that. I don't understand how if I leave queue during matchmaking for whatever reason I immediately get a timer but the toxic people that tell me to "drink bleach", leave game after feeding, and play league knowing they have garbage internet (seriously, they admit it) that affects their ability to contribute don't suffer any consequences. I work in networking and I refuse to believe that there is no way to determine that a game has been unfairly skewed in one teams favor. I refuse to believe that with all the computer science and coding experience and data that Riot must have that they can't figure out how to make the experience better for the people who get screwed over by this. I don't care if I come away from a game with 0 IP because some guy on the other team left. There no reason why I should have been rewarded 16 or whatever IP because the enemy teams tf and tryn left the game and the 3 unlucky people who were pretty much forced to sit there and play a game they had no reasonable chance of winning should lose rank.

This game isn't some 10 minute game of TD in Halo that people can come and go and the rank if you even care about it is determined by your own performance. This is a team game requiring a time commitment of 20-50 minutes and some degree of coordination and teamwork. If you can't sit through it or are gonna throw a hissy fit like a 2 year old who doesn't get candy at target because you got outmatched in the laning phase don't play the game. If you do, why the hell is everyone else punished for it. If the server the game is hosted on doesn't get any move commands from the guys sitting at base with no items who was 0% in loading screen, why does my team still have to play for 20 minutes a game where the probability of us winning in one optimistic case is literally:

P(top feeds hard) x P(mid feeds) x P(jung feeds) x P(our bot 1v2's and gets fed as well) x P(the previous four events occur consistently throughout the game)

I don't understand how this gets seemingly no effective attention during the patches but they hire people to sit there and say "darius q needs to do 10 less damage at level 2" because hes to strong or whatever. Just hire an intern from some local university to come up with an algorithm for solving this issue. I go to UCSD; you know how many of my fellow students would gladly work for free or minimum wage to improve the game they play every week and throw "wrote an algorithm that improved the gaming experience of millions of players" on their resume?

EDIT: Don't tell people to report the player after game. We get zero feedback as to whether our report even made a contribution to bettering our community. It doesn't take a sociologist to tell you that that isn't the way to get an entire group of people to contribute to something.