I can't imagine what was going on the devs head when they decided this would be a good idea.
Perhaps that basically everyone has a Facebook account and that catering to people who don't or who make a big deal about using it to connect within a social environment are probably not a worthwhile target market?
Or maybe they're tragically out of touch.
(I'll go with the first one.)
I would go with tragically out of touch, but then again maybe I'm sane.