More importantly it's a capability program. People and organizations who can build rockets, execute space missions, and have regular work doing so is necessary if you want to maintain the institutional knowledge and manufacturing capacity to do so.
That was a good argument in 2009 but it's a bad argument now. There are currently over 100 rocket companies in the US. Having those people work on dead end technologies like SLS rather than forward looking technologies like Starship or RocketLab Neutron or Relativity Terran R or Blue Origin New Glenn etc hurts rather than helps.
They are getting fractions of that. NASA funds small missions across a wide variety of such companies. It’s how SpaceX started. It’s been one of the most effective NASA programs ever, IMO.
The commercial programs have seen significant expansion in scope and spending as their benefits have become clear. The lunar landing contract to SpaceX is a great example of such.
Astra, Rocket Lab, etc. have to demonstrate capability to move up the ladder.
Again, I doubt it. NASA funding doesn't really work that way. They don't get a big bucket of funds to distribute as they please. SLS was the pet project of a number of powerful Senators, to the point where the joke is it's the "Senate Launch System", and has been specifically appropriated for by Congress.
There are ALWAYS politicians who are happy to give the money to their project. The idea that NASA budget would go down by 5 billion $ without SLS/Orion isn't really credible in my opinion. Some projects would be done, because Senators in space states wouldn't want the budget to just get lost.
Technically, yes, SLS can send people around the Moon, but gotta remember that Starship is very much on the critical path to the actual goal of boots on the Moon.
So, 'currently' is doing a lot of heavy lifting there, not to mention in general the idea of SLS being ready to send people to the Moon now is a bit of a stretch too since Artemis II will be ready to launch in 2024 if we're lucky, which is also when (if we're lucky), Lunar Starship should be starting its testing.
And high-end manufacturing capability is very important to have domestically from a defense perspective.
I recall some NPR story recently about war games the US runs about a hypothetical war with China -- it was said that the US loses most of the time in these simulations. Why? A lack of industrial capability.
