You get curation rewards as well as interest rate on SP. I don't self upvote, and neither with 10x or 100x more SP, I still wouldn't self upvote, just because of moral reasons. By helping others now, you also increase the value of Steem later, because this builds a strong community.
RE: Applications Team Update: Hivemind/Communities, Sign-ups, Developer Tools, and Condenser (steemit.com)