Government employees' work by law is in the public domain: "Copyright protection under this title is not available for any work of the United States Government

Government employees' work by law is in the public domain: "Copyright protection under this title is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise." (17 U.S.C. § 105) "A 'work of the United States Government' is a work prepared by an officer or employee of the United States Government as part of that person’s official duties." (17 U.S.C. § 101) ...although I disagree that the pressure to give away copyright is weak. At least in the life sciences, the prestige you get from a publication in, say, Nature or Science is far more valuable than the work alone.