> Everyone who's not terribly worried about privacy always uses the line 'if you're not doing anything wrong, you have nothing to worry about'

The right way to reply to that is: not everything that's legal must be public.

You probably don't want the rest of the world to see you poop, or pick your nose, or listen to every word you say. Almost everyone has things they'd be embarrassed to disclose to other people. And this can be weaponized against you should any rival gain access to it.