The original sport utility vehicle was a truck with seats. A separate ladder frame, a body bolted on top, low-range gearing and enough ground clearance to make use of it. The Jeep Wrangler, Ford Bronco and Toyota Land Cruiser FJ are still assembled on that principle. The large majority of vehicles now wearing the badge are not.
What divides them is construction, not size. A crossover takes a car’s unibody structure and raises it; a body-on-frame SUV keeps chassis and body as two separate things. That makes crossovers a subset of this tag rather than a rival to it, and it is why a Toyota RAV4 and a Wrangler share a category while sharing almost nothing mechanically. Manufacturers stopped drawing the line decades ago and market both as SUVs. This tag follows them, and the crossover page carries the distinction for anyone who needs it.