I went back through that old, massive discussion from the beginning. Not 100% of it—I skipped over some bits too.
We had started with Anogeianakis’s text, which argues that at some point folk musicians had almost come to feel ashamed of their art, and that the lute-guitar came along to meet their “need” to appear more modern without having to learn the guitar proper, a new instrument.
I wonder whether it came to meet completely different needs:
Is building a guitar soundbox—with a two-piece back and two sides—not simpler than building the lute’s bowl, with its staves and all the trouble they involve? That’s where the whole comparison lies: in the soundbox. The soundboard and the rest of the instrument are more or less the same in the lute and the lute-guitar.
So if it really is simpler to build, could the lute-guitar simply have been the instrument makers’ solution for being able to sell cheaper lutes (and therefore more of them), and, correspondingly, the instrument players’ solution for buying cheaper lutes?