I think it's very simple. If the general public(middle class)really sees what is going on with tax loopholes for the rich and how much they don't pay in relation to the % they should be paying some independents will be shocked , angry and might take it out on him at the polls. I just think he realizes that disclosure will hurt him more than hiding them from us. And please I am also not saying Romney did anything criminal,what's criminal is a tax code that allows the many loopholes for what seems to be only the wealthy.