There is incentive to keep money as steem for steem power. The price of steem recently rose from about 30 cents all the way up past 2.00, and I only see this trend continuing. Steem is in the process of developing other apps that will allow more users to be involved without them having to be a decent writer. Once the site population grows exponentially payouts may be reduced generally speaking but people will still be excited to earn money for something they were previously doing just for attention. For now, Steem's future is looking pretty bright.