[aleph_minus_one]

Explaining this in sufficient detail would make a really long text, so I'll just give one very isolated point:

Bascially, the internet is a dark forest. A lot of things "ordinary" people do all the time is insanely privacy-violating (just to give one example: if you send a message to a person who is not insanely privacy-conscious and capable (meaning very knowledable about technology) of preserving your privacy, malicious entities can spy on you).

So, for the product/OS to be capable of keeping your privacy, it will have to prevent you from doing an insane amount of things against your reflexes, comfort and what you learned about politeness.