Maintaining and testing such an app has costs and risks. They may think it’s more secure that signal does this. It is also harder to attack all of signal.
They are also significantly resource constrained, everything they have goes towards defence. The effort building the app could be deployed on developing weapon systems they can’t buy.
Your right nations should have their own independent systems for secure communications for military, politicians and civil service.
Maintaining and testing such an app has costs and risks. They may think it’s more secure that signal does this. It is also harder to attack all of signal.
They are also significantly resource constrained, everything they have goes towards defence. The effort building the app could be deployed on developing weapon systems they can’t buy.
Your right nations should have their own independent systems for secure communications for military, politicians and civil service.