NASA just realistically isn't a launch provider. SLS began development in 2011 and has only flown twice since 2022. It's has cost them almost $32 billion to develop. It even uses quite a bit of older hardware despite all the development costs.
Compare that to SpaceX's Starship. It started full development in 2019, has cost $15 billion to date, brand new everything, fully reusable, developed arguably the best engine ever made, has flown multiple times now (to varying degrees of success).