A green lasts you a day in a new expansion before you inevitably get a blue, and blues are just known to be immediately replaced by epics first 2-3 weeks you hit max level, so what's the point of these anymore? Moral masturbation as you get that small mental high of seeing an upgrade in color of your gear?
I don't know, this whole system is behind the times. It made more sense in pre-BC and BC because the gear was a lot more gated since there were a lot less options to get upgrades, but nowadays what's the point really, aside from epic -> legendary.