From a recent post by Dr. Paul Spudis, “'Where, Why and How?' – Concerns of the House Subcommittee on Space“:
An interesting moment in the hearing came when Squyres expressed concern that even if the Space Launch System (SLS) is completed, there will be no money to operate it or provide payloads for it. I believe this concern comes from a misunderstanding of the fundamental purpose of the SLS – the launch vehicle mandated in the 2010 NASA authorization bill. I have written previously that because of the peculiar wording of that bill, there may have been an ulterior motive involved in such specificity, viz., that the SLS is Congress’ way of retaining a semblance of spaceflight capability within the agency, a national technical capability that they believed was discarded with undue haste and little serious thought. In such a scenario, the operational cost of SLS is not relevant, at least until an attainable, strategic horizon is recognized and adopted by a future administration. SLS is merely a mechanism to retain a national capability and operational spaceflight team, the hard-fought-for-and-won national treasure of space expertise which otherwise would be scattered to the winds.
This paragraph highlights for me the difficulty of decision making in the public sector.