I think the fear abuse victims have when they are young about others finding our their plight get's carried over as an adult which is why it is harder to maintain relationships. There is also the fact that socializing and maintaining friends as a teen is fairly easy, especially because as teens people are not sophisticated individuals so friendships are more often made based on common interests rather than mutual compatibility(my personal two cents on this, I am no psychiatrist). There is also the under developed social skills from the recluse lifestyle most abuse victims take in at a young age.