I think mental laziness on the part of the prospective "business" partner has a lot to do with it (speaking from that side of the equation). I've held off actively searching for a tech co-founder until I've run with the idea as far as humanly possible: customer validation, half-assed web mockups, etc. Sure, your results may not be as robust as if you had built a v1.0 product and put it out there for iterative development, but since that isn't an option, stop whining and get creative!