When Amir says, "There are a lot of children in Afghanistan, but little childhood," how does it relate to Sohrab?

Sorhab had no childhood. After his parents are murdered, he stays in an orphanage in Karteh-Seh. Then he is a sex slave to Assef until Amir rescues him. Sohrab tries to commit suicide after Amir tells him he may have to stay in an orphanage again. Sorhab never really had a time of innocence.