There's a reason SLS is nicknamed the Senate Launch System -- Sen. Shelby of Alabama rains fire down on any NASA official who comes anywhere near observing that

There's a reason SLS is nicknamed the Senate Launch System -- Sen. Shelby of Alabama rains fire down on any NASA official who comes anywhere near observing that SpaceX could fulfill any objectives allocated to the SLS. It's as much a pork barrel, to use the political lingo, as it is a rocket -- a steady source of jobs for Alabama and a couple other Southern states for as long as it's in development / production. And no one cares enough to take on Shelby and his allies. So, rational proposals like using SpaceX are sadly political non-starters at the moment.