There are pretty clear, practical reasons you might want to control the client of a commercial network service.
You can still argue your case, of course, but phone companies are a bad analogy here.
Only because it's next-to-impossible to call the API, because of the way they lock features to their client!
It's by societal consensus that this can be made fair, and to convince people that it is fair, there needs to be a logical, indisputable argument that it's fair. Otherwise, the service providers can always just hide behind the counter-argument of being in control and TOS etc.
This seems to make it pretty clear they don't want you to create 3rd-party clients for their service.
"You may not create derivative works based upon any of our services"