They are if you use their service. You agree to their terms when you want the services they provide. Of course, you can violate the terms of service, but that

They are if you use their service. You agree to their terms when you want the services they provide. Of course, you can violate the terms of service, but that puts you in the wrong legally and potentially morally, depending on your specific moral values. You aren't entitled to their service, but they are entitled to your data (as allowed under the relevant jurisdiction) if you choose, of your own volition, to use their service.