They are jerks, who only care about themselves. For them, their lane is all what they want and they never care about how is their teammates. Well, if they are like Leon who can carry in late game even when all other members feed then it’s OK for me, but it turns out they fed 1/10 after taking the first turret at 15:00 then rage ping all the time then… it sucks.
P/s: I successfully make Leon lost a game even though only me fed because he last hit everything in jungle. So if you are smart you can make your whole snowballing team lose with only yourself. And no, feeding non stop under turret won’t make it work.