I don't throw out wooden spools. They're not making them anymore except one company (YLI?) for quilting thread. But generally they haven't been used in ages.
I don't have many either though. I generally only get them when I buy a machine that has one or two with it.
Old bobbins only get trashed if they're too far gone to salvage. Rust cleans off but bent and warped ones are generally not worth trying to fix.
Exceptions would be rare or expensive ones. Those are worth the effort to try to save.
Rodney