Privacy is about thoughts. It is impossible to fully know the mind of another person. Without that knowledge, a person's thoughts can never be fully put into context. If all thoughts were made public, all human beings would look like monsters or mentally ill to each other. This is why privacy is necessary.
So its not just about protecting people's thought, its also about protecting peoples thoughts from being fiddled with by fools too dumb to fully understand how dumb they are.
Which is why privacy is about power and claiming our own territory for our thoughts. It's also about testing different ideas out before they're made public so that the ideas have been mulled over properly in a safe space, un-judged by the masses.
No, not always.
Insisting on there being no cameras in your bathroom has nothing to do with thoughts. It's barely even to do with information: you'd be unlikely to really learn anything consequential from those cameras. It's still a matter of basic privacy.