because the devs clearly balance progress around the total available from world quests. they assume everyone does them and set rewards accordingly. maybe if they increased the spawn for 10.0 it wouldn't hurt that much, but you can bet your !#@ that for 10.1 they'll take them into account when they put in the inevitable progression gates. also, a lot of things like professions, which is a big part of this xpac, are gated behind renown. it's not as optional as people are making it out to be. maybe if it was just xmogs, dragon customizations, and pets, but it's not.