"human error is an issue so we're going to make it so manamune can never be turned off"
except the issue was people who never turned it off, why the hell would you spam an item that consumes your mana on needless things like farm or jungle camps?
the only time you would even need to use it is on enemy champions or baron/dragon.
this is just to push the "give blue buffs away" agenda
whats next people gonna have no mana because human error can cause you to run out of mana to fight with?