Privacy Laws

You know the federal censuses are protected from general public examination for 72 years, under the requirements of the U.S.privacy laws. So I'm trying to figure out why databases, such as the Minnesota Birth Index, are online and cover the 1935-2002 time frame and all of that data isn't protected? I can put together whole families with a few searches and have vital data, such as mother's maiden names in mere moments? Now don't get me all wrong- I can use the data as a researcher but why is there a seeming double standard? What do you think?