People who don't own the content are the ones willing to sell you the product, not the owners of the product. The TV signal is not the product. It contains the product.
I own a truck and carry a load of CocaCola from Atlanta back home, I cannot legally sell it retail (or wholesale) to anyone because Coke has an exclusive contract with a bottler here. I own the truck, but do not have the right to distribute the product it's carrying.
Satellite companies do not own the product.
I don't get what is so hard to understand here. If the people who OWN the product wanted to allow it, it would be very simple for it to happen.
If a channel is able to buy national rights to a program, then there is no problem for them to sell their signal nationally.