How come AFK’ing is such a big part of playing Minecraft.

How come AFK’ing is such a big part of playing Minecraft. I mean how can Not playing the game be such an important part of the Game. I know it’s to minimise Lag. But the world is fighting Climate change, and at any given moment thousands of computers around the World are running, for no other reason than AFK’ing.
It’s not Okey and should be fixed.