More info in the FAQ. And Derek knows that he won't. Camping in Style Family camping trip. Someone looking at him like she wants him. Supernatural Beings are known, Sheriff Stilinski is a bad person and a parent who owes money, lots and lots of money, that he doesn't have and can never make, to the biggest names in town, so he gives them the only thing he does have, his four-year-old son Stiles.
Derek thought it was because of Stiles's similarity to Paige.