NASA works with Spacex, Lockheed Martin, Northrup Grumann, not by itself.
Sorry NASA has been forced to work with SpaceX because the primary contractors that it uses have not been delivering. SpaceX does not build their rockets and crew craft to any NASA specifications, SpaceX designs and builds to their own needs and so they have surpassed of NASA's traditional contractors. NASA relies on SpaceX just like it does on Russia for its rocket engines. NASA's new boondoggle Artemis will launch today using "dirty RuZZian" engines.