e2e encryption isn't something you add as an "optional feature", but rather, something that should be in the design from day one, for all communications (mandatory).
I feel like this is the goal, but as unfortunate as it is now - that's not the case, and adding E2E encryption of any sort should be celebrated to perpetuate the idea that it's not an option, but a need just like adding authentication isn't an optional feature.
>just like adding authentication isn't an optional feature.
As an added note, authentication can be and should, for most cases, be done on a session basis, when establishing the session key (which should also, by the way, be generated with care to provide forward secrecy).
The idea is that if individual messages aren't signed, there's the advantage of plausible deniability to third parties. You know who you're talking to, but you can't take a message go to a third party and claim "hey, this person has said this. See? This message is signed by his key.".
This is the level of privacy generally expected in a conversation conducted within the same room in meatspace, and most people would be uncomfortable with any less than that.
