Why is it so hard to find a good used Suburban 2500

Finding a heavy tow vehicle that hauls a lot of people is challenging since none are in production now. I didn't realize how challenging until I sold my 15 passenger van with a V10 a few years ago at twice KBB value($7800). I had people competing for it and willing to drive 8 hours to come pick it up. I have heard that the Ford Excursions are tough to come by to.