Lol, you joined the forums in 2011 and don't know?

Tanaka said having crafting classes released in intervals would cause a problem with economy and therefore released all crafting classes together to alleviate future economy problems that would arise otherwise.
So my personal argument is this, if we're still stuck with classes, we're stuck with the same crafting classes forever. Tanaka still haunts this game until several 1.0 elements are removed.