You probably don't see it much because other than people transporting used cars, not many have a reason to do it.
I do see it fairly often, not necessarily using a truck or SUV as tow vehicle, just one car towing another. You just might not be looking for it, or it may not be a common practice where you live or where you drive.
Used to be a lot more common when we could tow cars bumper to bumper, but now most have hidden bumpers behind a plastic fascia, and often the bumpers are designed to collapse under fairly light loads, so that both vehicles need add-on towing equipment.