Elixir is your offense budget
If gold builds your defense, elixir builds your attack. Your Laboratory — where every troop and elixir spell is upgraded — is the single largest elixir sink in the game, and elixir also pays for Army Camps, Barracks, the Spell Factory and your elixir collectors and storages. A maxed army with under-leveled troops is almost always an elixir problem, not a strategy problem. This service keeps your elixir storages full so Laboratory research and troop upgrades run back to back instead of stalling between raids.