If it was gone it would be one less thing we'd have to balance champs around. We could just focus on balancing champs around their cooldowns instead of their ability costs. Almost no one builds this stat anymore anyways, so why not just get rid of it?
Smokin Penguin4 votesso why not just get rid of it?
Because these guys would break the game: 
Cloud2732 votes[{quoted}](name=Smokin Penguin,realm=NA,application-id=3ErqAdtq,discussion-id=1EhWqhep,comment-id=0001,timestamp=2018-11-16T00:55:26.846+0000)
Because these guys would break the game:
And manaless champs sitting in lane forever is so much better right?
ankoanko192 votesAnd manaless champs sitting in lane forever is so much better right?
Energy users are also relient on their.. energy. And manaless champs like Aatrox and Riven sacrifice crucial things inorder for them to be manaless.
TheSingularity1 votesThey sacrifice range somewhat, not much else
ankoanko191 votesThey sacrifice range somewhat, not much else
bad Range & base stats, telegraphed abilities. Some spend their HP instead. Some also play around it 
Dope Solo1 votes
???
Death by Glamour1 votestbf after 12 mins mana isn't really a problem for anyone
Tr4shB4NSYST3M1 votesLmao you forgot 
, level 1 in lane she wouldnt even have to auto- Snek EEEEEEEEEEEEEEEE first blood
5050BS2 votesWhat if we made all champs have the same mana pool an abilities cost the same mana?
ankoanko192 votes
Doesn't sound so much fun now, huh?
Der Lindwurm2 votesI think they should just give mana to everyone.
saltran1 votesWhat if we made the game only 5
vs 5 and only using the default skin?
Dope Solo1 votesPeople would hate it. 
. The game would suck. Better to give all champs a mana requirement.
Agent Corgi1 votesMost if not all champions are Balanced around Mana, some are even "Gated" because of Mana Costs. Imagine if Jayce could just pull out Accelerated Shock Blasts more often or if Sion could Constantly throw minions at you without end?
Trust me & everyone else here, Mana is extremely important balance-wise & simply getting rid of it isn't an option.