Because low elo players can't carry without damage, and since almost everything is balanced for them, heck, even when they nerf for LCS, most of the time they leave what makes the champion good intact and nerf something else because otherwise low elos can't play that champion anymore.
What's the mantra in most recent years? "The skill disparity between players who mastered the champion and players who didn't is too high, so we're making it easier to play".
Why did they add Zed, Darius, Garen to the jungle? To make low elos want to play jungle more, that's exactly why, they even stated it. Instead of buffing champions who really need it and are junglers by default, they add laners there to make it more appealing for lower elos.
Everything is done to please the bad players, hence why damage is rarely nerfed and damage itself is buffed to solve problems. 90% of low elos can't carry with beef and CC unless that champ is overpowered by nature, they also can't carry with skill or macro, only with damage.
There's your answer.