Because every other girl is interested in Tim. Except Cass Cain, who's into terrorists (Black Wind), kinda dumb superclones (Conner) and people who stalk her (Zero).
Oh, and Sal. Who Beechen felt would be a good match for Cass by making a male duplicate of her minus the winning personality. Seriously, beginning a conversation with "My dad was beaten to death in front of me when I was seven and I went mute for several years" isn't exactly an icebreaker.