Unfortunately people don't see voting systems as a method to highlight the relavency of a contribution. They see it as a like/dislike system, and so I see as shut up signal used by most because downvoting a contribution buries it to the bottom where few people will see it.

If it was used for relevancy and quaility then communities would be self regulating by the users. I believe Reddit's guidelines state(s/d) it's voting system was meant to be for relevancy, even though most people use it as a like/dislike system.