It's true that no one would send a gift to an unknown person, but perhaps you would like to send a gift to someone you know only online, for e.g. someone might have helped you out on an online forum or someone's blog post might have helped you out or you might have met someone online in a chat room perhaps etc.
This is true. Patio11 has Halloween Bingo Card Creator, so why not "SecretSanta" themed gift buffer? Nothing says that the recipients of the gifts can't know each other offline, but the gift giving process is what needs to be anonymous.