Because it was selected on the basis of what spending it could justify (in particular, that it would give the SLS something to do), not on the basis of the value of any technology produced.

I’ve come to see this as a feature not a bug. To get a significant amount of money from elected officials there has to be a there, preferably their district. SLS was the giant scaffold that allowed for the effective seed of commercial resupply missions to occur and grow. Without SLS’ distributed network of Government friendly contractors and contracts all lined up in an immaculately conceived waterfall the focus would be on the commercial efforts which have to be run a different way to get better results. Imagine instead of Joe Rogan, Musk is spouting off to some committee of crusties. That wouldn’t be pretty, and success means avoiding that conflict in world views by funding SLS. In some ways it is kind of like funding a semi-fake cathedral in order to attract and develop the bazaar you really want.

It's a feature if you're feeding at this particular trough. It's not a feature for the nation as a whole. It leads to money being squandered. The goal should be to benefit the nation, not maximize a budget line.

Is the effort to build a scaffold squandered since it is used to build something but is not the thing being built? I'd rather see economically sustainable off-Earth enterprises built without a scaffold but I'm not so loss averse to take nothing over something.

If the technological advancement is funded by a private entity (whether or not for a profit motive, there needs to be no such justification). If it's public sector you need to at least come up with some public benefit excuse for it, jobs program is a bit of a steel man for the political funding of a science program. If you want your science to be free of that entanglement you should be figuring out how to fund more things like Glynn research ltd.