I once was asking Panasonic support about the effect with a MFT zoom lens and support replied that the lens actually has "mini gyros" that spin.
Also for the zoom lens the sound becomes more noticeable when you extend the focal length.
I think two aspects were not mentioned yet, so I'd like to add:
When taking movies while moving the camera, you typically do want to have no image stabilization.
Otherwise your movies may look "jumpy" (the system stabilizes until you exceed the movement limit, then it re-adjusts) instead of smooth.
However some system allow vertical stabilization ...