Phone calls aren't encrypted either, if you think about it [1]. There's a large expectation of the telecommunications industry to be able to perform legal interception, and providing end-to-end encryption out of the box might be seen as a direct violation of that requirement.
[1] Except, somewhat incongruently, between Google Fi subscribers on some Android phones: https://support.google.com/fi/answer/11295314?hl=en – no idea how that came to be and how it even works! I suspect it just upgrades to a FaceTime-like VoIP call.
[1] Except, somewhat incongruently, between Google Fi subscribers on some Android phones: https://support.google.com/fi/answer/11295314?hl=en – no idea how that came to be and how it even works! I suspect it just upgrades to a FaceTime-like VoIP call.