SBI votes are small, but daily and for life. They add up over time and the voting power of each group will grow over time if people upvote SBI. They take the SBD and SP earned and lease more SP and purchase SP to increase the voting power to help everyone. As an added bonus those that upvote SBI get a larger share of the daily votes. SBI isn't going to make anyone rich, but it's just a nice way to get a daily vote on your content.
Hope you join in the Pay It Forward Curation Contest.
I'll vote for sbi posts :-) And will search what is the pay it forward thing :-)
Thanks for your answer