I understand it could be abused by someone just leaving to make sure the team gets less lp of a loss. But the system could automatically enforce something heavy upon a ton of leaves. No matter the intent of the leave or not, losing -17 lp for a game only to win the 17 lp back the next game is a hassle and makes it more difficult to climb the ranked latter. Literally blows my mind I have to lose the same amount I gain for a single game over an afk that decides he/she would rather get a leaver title.
The game allows for up to two leaver marks a week, so really its not like anyone cares at this point.