Most people don't treat Dropbox/Google/Facebook (non-public) usage as being equivalent to CCing the government but maybe they should.
Most people are worried about "disclosure" - which is something Uber violated for a PR stunt at a party recently - i.e. we're usually okay wandering past the window naked, because we assume it's extraordinarily unlikely that someone will be pointing a camera at it right then, or that it wouldn't be more embarrassing for them to try and yell "hey that person is naked in the window I saw them!"
Conversely, we wouldn't be happy if someone did take photos, then uploaded them to the web, and showed them to all our friends etc.
In a practical sense, this is how people act. It's how you have to act - it would be practically neurotic to act any other way.