1) There are many people in my life who would make it much more difficult if they knew how much I make. I've kept it from them for a very good reason and they're definitely the kind of people who would just go and look that kind of stuff about random people they know. This would tell them how much I have in investments and property as well.
2) It would necessarily reveal far too much personally identifying information or not serve the purpose you'd want it to. If I had ran away from an abusive or stalking relationship, they could simply look up the state and municipality I pay taxes in, and what company I worked for, making it almost trivial to find me. This could also mean finding (and targeting) anyone that works for a certain company.
3) It would be far too easy for companies to use this information for any number of purposes. I'm currently getting a huge amount of mail about moving companies and brokers because my landlord publicly put my condo up for sale. It could get much worse than that.
4) If I'm the daughter of an extremely conservative family but I'm working at a strip club, even if I'm "not proud" of what I do that give no good cause to expose it to the world.
These are the situations from off the top of my head and already it would reveal far more information than I'm comfortable with. "If you have nothing to fear than you have nothing to hide" is never an appropriate excuse to curtail anyone's privacy.