Which messaging apps are those? I have only seen such behavior for one-time photos, where it makes sense (although one-time photos are security theater because nothing prevents you from taking a photo of the screen with another device).

Requiring someone to have access to another camera is not "theater" if it vastly reduces the liklihood someone will be able to produce a copy.

It gives people a false sense of security. You think the other person can’t copy the photo, but they actually can.