It's stated specifically in the rules , this is to prevent suspicious users transferring hijacked/stolen items without trace, and other small reasons.

Funny you speak of privacy when you are on the internet.

We never took away your so called "right" to privacy. To take it away would mean to give you no option of maintaining it. You have a 100% foolproof method to keep your backpack private, just don't use OP.

You have a right to a religion, do you accuse the church of taking that away if you become Christian?

Stop complaining.