Plenty of people had “private” LiveJournal accounts back in the day with no expectation that it was a zero-knowledge system. Just that they weren’t sharing it. I may not be a good indication of “most people”, but I just don’t think that most people think of privacy in the way that we (folks who know details of encryption and metadata leaks) do.
But that's the problem, isn't it? I mean, many people do (sort of magically) think that their online stuff is private. And then they get pwned in one way or another.