By getting a small subset of players to buy premium cosmetic content and in-game gold. Blizzard came up with a clever mechanism involving game time and other players for the latter, both in order to obfuscate what they were doing somewhat and to give them a little more control over their economy.
That is exactly why subscriptions had dropped sharply after the release of Warlords of Draenor. (the endgame was designed around the antisocial garrisons, a mistake which they have scaled back in the upcoming expansion)
Ultimately, you don't matter to them. For every subscriber like you they lose because of a change, if they get two more, more casual players to sign up, they're in the black and sacrificing your membership is rational from a financial perspective.
The Blizzard Warcraft Store: https://us.battle.net/shop/en/product/game/wow
Information on the "WoW Token" mechanism for turning $ into gold: http://www.tentonhammer.com/guides/guide-to-buying-and-selli...