A matter of ethics
One again, in my opinion:
In the private sector a company sells a product or service to a client in exchange for money. The money the company gets can be considered the company's at that point. In the public sector the money comes from the citizens and the government is entrusted by the public to wisely administer these funds. If the private company makes bad decisions and squanders its own money it has violated a trust to its share holders. If the public sector agency makes bad decisions and squanders money entrusted to it, it has violated a trust to its citizens. If the private share holders let such a situation continue the company will go out of business. In the public sector there is little threat of bankruptcy and we call the coverup of such incompetency corruption. In the private sector there are legitimate trade secrets about mistakes that may sometimes need to be kept secret from the public, as long as SEC rules are followed, in order to protect a company's image. In the public sector keeping such secrets may be a violation of the public trust. I believe it is unethical to coverup such bad management practices.