Why do you need to lvl to learn professions?

In some ways it's to keep players in a sort of bracket so that their level not only matches the items their making, but keeps them around areas that have the materials they'll need for those items. It helps guide players through their profession, and realistically the vast majority of players are never going to see anything that would even indicate they need to be a specific level if they're working on their profession at a moderate pace.

In addition, not only is it weird for a level 20 to be crafting items that are for level 60 players, it encourages people to create level 1 characters simply to produce some specific items for that profession. That doesn't help encourage a healthy economy, and it doesn't add anything to the game, in fact it takes a lot away from it. Continuing with that design philosophy we have always felt that disenchanting needed to adhere to specific level requirements to disenchant higher level items, and that change is being made.