The reason to sponsor as many as possible is because many just sign up and never do anything, or they lose interest for some reason, or may even think this program is to good to be true, which is isn't otherwise I wouldn't ahve been part of SFI for 8 years now.
But just getting as many affilates as possible doesn't matter if you don't communicate with them or give them guidance when they ask for it. Communication is the key!