Why do execute indicators exist in the game?

It completely removes the risk of fucking up. And the fact that some champions have it and some don't makes literally no sense. Like for Chogath. As long as you actually look at the indicator it's impossible to misuse his ultimate. It's a completely guaranteed kill if you land your Q. Pyke for example as well. Why does he get indicators when he can execute people? And then some champions like Darius or Garen don't.

League is supposed to be about making these kinds of decisions. Putting the indicator in the game is just unfun, and it decreases any chance of messing up the ultimate, which reduces the possible human error existing on that player's team. This then skews the chance of winning (meant to be within 1% of 50% at all times).

"But those champs take other skill to land their other abilities, it's a reward for them!!!" is a champion who is required to land a stun, a 1.2s delayed skillshot, and another skillshot that can be blocked by minions. He also does not get an indicator of execution.

It's not even broken in the game. It just makes no sense. Either have every champion get one or have no champion get one. The game is wildly inconsistent with things like this and it's annoying.