Once upon a Hub... the up and down votes used to be viewable. (this was a few years ago when they were first added as a feature) And instantly, everyone became obsessed about them, especially down votes. People wanted to know just who was voting them down.
And thus, admin decided to make that info not viewable, and have since said that it's just a tiny fraction of what goes into a HubScore calculation.
So, to go back to your original question... very little happens when someone votes a Hub up or down.