It's not really supposed to, is it? There are plenty of parts that could make a profit, but we prefer the government providing stuff for free instead. For example, if the federal government were allowed to hold copyrights, it could make good money licensing all sorts of military photographs (WW2 photography alone would be worth quite a bit). And the rate for interstate highway travel that the market would bear is probably higher than $0.00/mile. Instead photographs are public domain, and highways are free.