Because having your human space program depend on a single launch provider is not great? This is not a SpaceX dig: for years, NASA had to rely exclusively on Roscosmos,and that wasn't ideal either.
NASA can "waste" money now and ensure there's some level of competition across the board later, or be subject to gauging in each specialist niche in the future
NASA is a political organization created by politicians for political purposes and remains beholden to politicians for its continued existence. The engineering innovation, science, and exploration of NASA programs are wonderful side effects. The bad news is that it’s always primarily political but the good news is that as long as the political purposes remain relevant then the overall budget is reasonably safe. With competition with China, and the burgeoning commercialization of space its relevance is likely to grow.
Thinly veiled welfare or a grandfathered in earmarks depending on your perspective.
I think this will be a much more pressing question (if?) after Starship starts flying regularly and finishes its demo mission to the moon as part of its Artemis obligations. It's easy to rationalize SLS with whataboutism while Starship is in development - particularly since SpaceX favors a hardware rich style. I'm not saying that this is good decision making, just that the arguments are plausible - the fig leaf is dense enough to do its job.
But if Starship is able to achieve and/or surpass the flight rate and safety record of Falcon 9, it'll be much more difficult to criticize; and consequently, it'll be much more difficult to support continued SLS development.
> I ... would have like to see NASAs stop shovelling good money after bad.
I too would like to see that. But I'm not particularly optimistic.
All indications point towards the opposite - that he considers low cost and high performance to be more important, and that vertical integration is an important part of achieving both of those goals.
While it's true that SpaceX is doing work in CA, FL, and TX, there's not much indication that they'll be farming out subcomponent work to high-40s number of states ala the Shuttle/SLS.
SLS is a worse system than Apollo, if anything we have regressed.
Given falcon 9 has been launching crew dragon for a numbe of years, and Starship is the selected lander, and falcon heavy exists for heavy lift, why continue with the SLS?
I for one will enjoy watching the launch, and am excited by humans travelling to space, but would have like to see NASAs stop shovelling good money after bad.