I could imagine small companies that rely on these boards and that also have their fab and sourcing pipelines set up would be able to easier source these themselves. Just have to generate the Gerbers (fabrication output format most manus need) and then send it off as part of a larger order, etc.

Especially if you're able to replace certain small/passive components with those you already have in bulk, it could be a potential cost cutting measure.

Just a guess though.

For my case, they'd be useful if I wanted to know how certain subcircuits are designed or laid out.

Even for beginners, taking it into kicad, enabling the selection of only tracks and vias and deleting them all, then doing a full re-layout of the board as practice would be a cool project if you're wanting to learn.