Certainly, yes. Making terrain and scenery from scratch has possibly become the thing I enjoy most about this hobby. I’ve also scratchbuilt a few vehicles, or at least the main hulls of them.
That’s not to say I go out of my way to scratchbuild something if it’s already easily available. I scratchbuild sometimes, hence it’s part of my hobby.
I’m also not very good at it. I’m in awe of the people who can make sci-fi mechs out of plasticard and the odd bit of putty.