Did Riot ever explain their nerfing of champion mana regen across the board?

Like for real, Grail is in a horrible state right now as an item and Morellos just got nerfed. Do they want everyone to have to rush these items? What is their intent? Why should mages have to invest in regen not because it might be desirable in certain situations but rather as a necessity while energy or C/D based champions just get to begin building damage immediately?