Because RED is not in the business of selling tripods, dollies, jibs, microphones, lights, etc.
RED sells cameras, and the accessories necessary for operation of those cameras; lenses, batteries, viewfinders, etc.
Should you opt to purchase a RED, be aware they are very heavy, so you'll need a heavy duty tripod to handle it. And along with the heavy duty sticks, you'll want a high-end fluid head, or a gear head. And if you're thinking about shooting hand held footage, your camera operator had better be in shape, running around with a red will get tiring quickly.