Well, one option is that, so far, the only beings who have urges are those directly using a Primordial charmset: the Primordials themselves, the Akuma, and the Green Sun Princes. Perhaps the urge is one of the things that all users of a Primordial charmset must have, or at the very least all users with free access to such charms.
Additionally, there's quite a bit regarding the Exaltations that the Incarana don't have control over by design: remember, they were worried that if they did have more direct control, that the Primordials could somehow use them to shut down the rebellion. The Yozi are not under such a restriction regarding the Green Sun Princes, and in fact have set things up so that they have much more control over matters than most other factions.
Additionally, the deal offered to Humanity was pretty sweet: at the time they were at the absolute bottom of the food chain. If they won, then they'd be moved to the very top. Many heroic individuals as Exalted defines the term would agree to those terms.