It might also have to do with the fact, that in kit form the convertibles are just more fragile. The Windshield Frames bend and break, and interior detailing was not the forte of many builders, years ago. I think there are many reasons, why hardtop/sedan kits sell better. And, I suspect that if were to ask questions at an NNL, about the preference many modelers could tell that they were less comfortable with convertibles but, could not articulate exactly why.