I agree too...it's fun to build and make things work. I tend to want props that function instead of just look like they do.
Also, while I like resin castings for what they are, they're ultimately a solid chunk of material that's been painted. They're not what the "real" item would be, they're sort of a life casting of the real thing.
I hope that in the near future inexpensive 3D printers will evolve to the point that they can print items that are hollow but sturdy and have a finish that's smooth. Then we'll need software that can convert a 3D scan of an item into the correct shells and turn out things that can be made functional with internal electronics, instead of a hunk 'o resin. I know this technology already exists for the business market but it's not quite read for the hobby market.