To upvote the content of others that you deem worthy of upvoting. We could all just post 20 spam posts/comments vote them up and be done with Steemit for a day.

Again I don't want to suggest that you are only using Steemit for selfish reasons, but I think a vote is something that is earned and given, and not something that should be used to boost your content to more visibility.

We all want to earn money here, don't get me wrong. But I think the rule to not upvote yourself should be implemented in a hard coded form :). There are still ways around it obviously but it sets a good signal, especially for new users, imo.