Peter, a lot of vibration can be due to steppers, but certainly not all.

Material cutting can induce problem vibrations resulting in chatter and poor surface finish. This is usually much more obvious with metal machining than wood.

There are a plenty of papers on use of epoxy granite in machine tools.

I agree that quantifying the effect is non trivial for the hobbyist and usually not done.

The same can be said of much of DIY machine design. Many design choices are made based on lack of understanding, what looks good etc rather than relatively simple good engineering principles.