we not all working into architecture and building world. Im creating site plan for event and production stage design. I have huge library of stage equipment that I accumulate along many years. No I don't truss my customer. They intend to use my library and stop calling me once they have the tool and the knowledge to bypass me. Entertainement business is a jungle and not sharing your skp is a surviving argument. When we were all using autocad, the complexity of learning this software create some sort of protection, but even then, its been a subject of conversation for years. Folks on Solidworks seem to have figured that one out with the .eprt extension. I don't understand why sketchup couldn't do the same.
and others have figured out how to convert them to .stl and other formats…
there is a plugin for Sketchup to export .stl
but how the client would read it? Reimport it in SU?
The easy solution is not to give away 3D models. Just give 2D images and "construction documents"(meaning whatever the client needs to build/produce it) in 2D formats (PDF, DWG...).
For an architect wht he should be seeling would be his design, technical and management skill, not his libraries, drawings or models.
However thats not what happens everytime. Not all customers are trustworthy but you still have to work.