I'd assume it's a combination of not knowing about the option, the cost ($2000ish?), and nervousness about buying something this expensive sight unseen.
Yeah, its hard being on the west coast and PNW in particular, still being hit with ADMs while Acura allocates ITS to places where they can't even move 'em.
Why wouldn't they? One's a little sportier, one's a little nicer. They're different, but pretty close. Especially if you're looking at a CVT Integra you'd be crazy not to check out the Mazda.