If you remember, you've read this in Launchpad Day 2.
A refresh: https://www.sfimg.com/LaunchPad/Day2
Too long to explain. Check this:
https://www.sfimg.com/Reference/SFIInternational
and not to forget, to answer to your question, please read this;
https://www.sfimg.com/Training/SpecialReports/DispellingSFIMyth
All the above will give you the answers as to why SFI is so powerful a program and why more and more people are joining every second, every minutes and every hour.