We live in a weird new era where I nearly always have full control of what information I share and whom I share it with (assuming I have an indefatigable interest in navigating permissions settings for my various social services), but I have no control over my information once it leaves me.
I don’t want my friends to be able to control my notification settings, and yet, I wish I could control their settings when it comes to my content.
Your content is your own until you share it, and then suddenly it’s the recipient’s content too, as a received message and intuitive privacy controls implies that a recipient should control their content.
The email design decision is less intentional and more an artifact of the information architecture of how email works in a stateless distributed early-internet design (how can you take an email off a remote server you don’t own? ), but it’s still an interesting design choice nonetheless.
