This argument is often trotted out, but it doesn't hold water if you think about it. There may be some examples where the technology has been re-used, but what'

This argument is often trotted out, but it doesn't hold water if you think about it. There may be some examples where the technology has been re-used, but what's their value in terms of useful research quantitatively, rather than hand-wavingly? Even if it's as high as 20% that can be re-used, you could get 100% of that value by researching image-sharpening, disaster shelters, food storage, wireless comms and all the other things you mention, directly. So you still have to justify the remaining 80% in other ways, the side-effects already accounted-for.