> And a screenshot, or another camera, or a rooted phone can easily defeat that.

Not if the message has already been deleted. Auto-deleting messages are so the recipient doesn't have to delete them manually, not so the recipient can't possibly keep a copy.

Exactly this. Even more: Auto-deleting messages are also that the sender doesn't have to delete them manually. Most people do not understand this. I even had a discussion with an open source chat app implementer who insisted on not implementing disappearing messages because they couldn't be really enforced.

That's a different threat model, no messaging app is trying to protect the sender from the receiver. Disappearing messages are meant to protect two parties communicating with each other against a 3rd party who would eventually gain access to the device and its data.

Wickr has a "screenshot notification to sender" feature (which of course, can be worked around by taking a pic of the screen without Wickr knowing you've done it).

What made you think I was pretending it doesn't?