Riot can you explain why you want mages to be the only class that has to rely on a resource?

ADCs-Mana costs are low enough that they'll never have to worry about mana. If they do just pick up a or to never worry about Mana. They'll use HP in trades but with how abundant life steal is right now it isn't an issue for them.

Tanks-Tend to also have low mana costs. is the only item they need to never worry about mana again.

Assassins-Most tend to be resourceless (for some reason), have low mana costs, or be shafted because they're a mage hybrid /.

Mages-Tend to have medium/high mana costs. Run into mana issues in the early/mid game. Are able to get rid of their resource dependence if they build items such as . With the new item change mana regen is going out the window and is instead being replaced by mana.

My question is why do mages have to be the only champion class in the game that has to depend on a resource? What is the design philosophy behind this decision?