If you see on the screenshot above of all the upvotes and curation rewards basically you can get curation rewards for upvoting. The optimal times to upvote a posts are from 25 - 35 minutes after the post. So a lot of people are running auto upvoters through stuff like www.SteemVoter.com to support the content creators they like when they aren't able to be at the computer and to just upvote automatically.