love it - is this a thing that's mostly used in government contracting, or do people encounter SBOM stuff more broadly than that?

You can encounter it when someone is doing due diligence while buying software company.

Also it is now hot topic because of CRA in EU.

I review an SBOM 3 days out of the week before lunch. If you can source your butter and cheese from the same dairy repo you can reduce the overhead of a grilled cheese by about 20%.