My (limited) understanding is this:
When someone cracks a game, the end result of their work may not be accessible or easily distributable to average users. Their focus is on cracking the game, not necessarily distributing the crack.
Others like FitGirl come along, creating launchers that take care of any dependencies needed for the game, and in general making it painless to run the cracked game. In other words, they repack the cracked game in a more user-friendly packaging.
If you've seen Breaking Bad, there's a similar dynamic there. Walter may be the one making the product, but he can't distribute it alone - he needs someone to make it widely accessible, if he wants people to actually use his product.
girthy gock