Friends-only posts?

So tell me, what is the purpose of friends-only posts? I mean, I get that some people put their fun links and quiz results as public and actual news as friends-only, but do you really think there are many people who aren't your friends trolling your livejournal? Is it just because they wouldn't care about the news, or that you want to keep it hidden for some reason?

Frankly, if I've got something "private" to write, I think it'd get saved to my hard drive, not my online journal. And if I wanted my friends to read it, I could email it to my friends.