It's because you can't give that information out without also granting write access to a person's life.

If there were a way I could give you my SSN/bank information/etc without also granting you the ability to impersonate me, I'd gladly do it.

Yep, but that's only true for some of those things. Others, like salary and photos of your kids, have other reasons for staying hidden (impact on social situations and safety).

Eh, if I didn't think my company would be upset with me telling you what I make, I'd let you know. It's not a big deal to me. You could probably figure it out based on where I live and what I do with my free time anyway.

As for pictures of my kids, I don't have any. But it's a pretty terrible argument because it perpetuates the false idea that you must want to hide something for privacy to be necessary.

I'd bet large sums of money Bruce Schneier has never used this line of defense against the "nothing to hide" argument.

If you work somewhere that's anything like places I've ever worked, then I think knowing your salary might have a bigger impact on some of your colleagues than you might think, eventually causing some blowback to come your way. Just my observation from past experience.

Yeah I know, but that's not my burden, that's theirs.

I'd also like to point out that I promised not to give that information away, and regardless of the privacy implications, I can't in good consciousness break my own word.

Hiding salary information is usually because it can often create awkward tension in your social groups. Like if your poor friends or family know you make a lot more money than you let show.

I know it's not the only reason for privacy, but it's a common and significant one.

Adultery, casual drug use, problems with drinking, what you said about your boss e.g he's a jerk, and a million other stuff.