Let’s see, so you’re telling me NO quests give transmog or armor rewards? Have you ever actually played the game? Did you buy your account off e-bay or something?
Ever heard of challenge mode dungeons? I’m guess you never even played Mists of Pandaria there were literally unique class sets around achievments of beating dungeons in a certain time… they also added unique weapon sets for the same types of achievments in Warlords of Draenor. Oh in Legion? There was a little something called Mage tower, ever heard of it?
Oh and plenty of the artifact skins were tied to achievments as well…