http://proxyoxiemywllckvpix543gqcmvvltrnb7inbwtk2knkehqt72tyfyd.onion/en/contact.html
Because it is not required and would be harder to implement. Read more on this topic at the Tor Project website: HTTPS For Your Onion Service . Why don’t you use the messenger “Threema”? One advantage of Threema is that users do not have to disclose their cell phone number.