Perhaps you should market more towards a co-founder then just a programmer. Or market as looking for a CTO? It's not really your fault that underfunded CEOs often think that they can lure someone in with the potential of a mega-exit, when that isn't the case.

I'm wondering if equity-only positions actually ever even get filled?

Good luck though, you're probably on the right track by not just hiring the first person in your lap (happened a lot at the last company. Bad move).