It's just marketing terms. Other manufacturers have tried other monikers and acronyms in the past, such as "Sport Activity Vehicle", in an attempt to differentiate their product from the competition. Perhaps "Crossover" will stick better than another alphabet soup... SUV is pretty ingrained in the common vernacular.
BTW, unless I'm crazy, there are other "SUV's" on the road that aren't build body-on-frame already, or at the very least don't use ladder frames.