Satellite communications are used for lots of things, but especially when people are in places beyond the reach of normal communications channels. On a boat, in the wilderness (or a war zone), or in a commercial airplane. They are critical links, but are also expensive and difficult to procure. That didn't stop Santamarta, though he did note that his lab conditions may differ from the real world.
Key to Santamarta's attacks were debugging backdoors, and hardcoded log credentials. Sometimes these credentials were obfuscated in some way, but never enough to stop him from figuring out how to use them. You might think it's a bad idea for companies to include these in their products.