Why should I reveal something about myself without a quid pro quo?
If I'm going to give information away I want some information in exchange. How about next to all price tags for products in any store, put the cost of the product next to the price? Would you be for that? How would you think everybody would react when they realized all shirts cost 39 cents, all pants cost 45 cents, all shoes cost 76 cents, even though all along we've all been paying $30, $50, $100?
It's an honest question, I also don't know the answer, but my point is the way people interpret information (as mobs) is outside of any one individual's control, and maybe people don't want to give that control up?