> For example chat history or email is important for the legal process. People need to prove conversations happened. I just send a whatsapp screenshot to my boss where my previous manager approved my day off. I could easily doctor such an image. We have the technology to grant someone access to part of a conversation in a legally binding way, technology just didn't mature enough, its to childish to do those things.

For whatsapp, they actually use the Signal protocol for messaging, which has built in deniability, so you can't use the cryptography it uses to prove a conversation happened, since any participant is able to falsify messages after the fact.