Sadly, I think there's just a psychology here around "self-interest". People are generally tuned in to "what's in it for me" and so will only vote for their own posts as it's in their self interest. This is a very short term vision and may work for a little while but as I've read in the comments, won't sustain the true value of Steem (or any other cryptocurrency).

The trick is getting people to care enough to read your posts and share their votes with your (or whoever's) content, not just their own. The long term vision would involve everyone helping each other to grow by overcoming that self-interest and thinking of the community.