As I understand, those contracts aren't legally binding, but they exist as evidence a company can point to in a trial to show that they tried to keep the user from doing X. An even more credible kind of evidence is actually making X technically difficult. Obviously they can't protect themselves against everything or they would go out of business (to use your example, they won't profit from selling stationary tractors). It's all risk management, and I'm not even saying I agree with their choices, only that their motives probably aren't as nefarious as Vice might want you to believe.