Votes only exist for threads with the "help" tag that are posted as a "Question" (as opposed to discussion/poll) which users are supposed to do when they're asking a question that has a definitive answer. Letting users upvote/downvote allows the best answers to be better identified.
I don't think there's a way to turn it off because it's a useful feature. But if you avoided making/viewing posts with question symbol you wouldn't see them (outside of forum suggestions).