Constant Trolls in Ranked/Leaving before 15

I'm just trying to understand why people who play ranked have to put up with people who go into games SPECIFICALLY to destroy the experience of others. I have been CONSTANTLY put with people who purposely feed or rage quit. The best part is People will come into the game stay around for 5 minutes THEN LEAVE. This FORCES people who are in the game to take the lose and lose LP. Im in love with the fact that there isnt even a system in place to give a Lower Lose of LP AT LEAST.