If I were to hazard a guess, I would say it may partly be due to the lack of transients, which again, goes back to the replacement of a physical process with an oversimplified informational model. In general, the ear is much more sensitive to the transient portion of sound than to the main oscillation. Many sounds can be synthesized with the same exact continuous waveform, but with different attacks, mainly due to the masking effects of the ear. Not to say Theremin doesn't have its place, but it has numerous issues and definitely deserves to evolve.
Thanks for the nyckelharpa video. I had definitely seen it before, but the significance hadn't been as strong then :) Seeing that inspiring performance in the context of this conversation was valuable!
In the past, I've been very conservative about avoiding corny and campy music tropes - there are way too many "wacky" novelty instruments, so I've avoided hurdy-gurdies, believing they had some kind of non-serious association (just listen to the name?!). As you pointed out, the leap from Electric Eel to Hurdy-Gurdy is almost trivial. So perhaps at some point I will loosen up and build some "digital hurdy-gurdies." In fact, one of my favorite instruments both conceptually and acoustically, is the autoharp. Perhaps I could combine the autoharp, nyckelharpa and hurdy-gurdy into something fresh.
In the meantime, I've been concentrating on that "transients and physical systems" problem. As we know, the traditional electronic envelope model, ADSR, is tremendously conservative and unashamedly uni-dimensional. Inspired by Venkatesh Rao's book, "Tempo," I'm trying to make a model of envelopes which is more like a weather system than bouncing ball.
Startup Nation - discourse on startups in Israel
Tempo - narrative strategy by Venkatesh Rao - REALLY good read, distilled and full of gold