IGLs Fragging ability

Why do players' fragging ability decrease when they IGL?

Enzo
Ethan
Munchkin (kinda)

Hard to focus on gunfights while directing people

doesn't prevent kinggg from dropping 50 while calling

as s0m said , if u are igling you are basically looking at the minimap most of the time and thinking about the next move for your team which supposedly and obviously effects your aim and focus on killing people