Yep, I agree. I personally like it being optional. Not end-to-end encrypted has an advantage of syncing messages to all other devices and use secret chats when privacy is more important than syncing.
Another feature I missed is ephemeral messages in secret chats: We can have messages automatically deleted after certain time (Although I wish the time settings are more fine grained).
Another feature I missed is ephemeral messages in secret chats: We can have messages automatically deleted after certain time (Although I wish the time settings are more fine grained).