Faerie lore:

The Fair folk are unable to exist on the island Manhattan due to the steel used in skyscrapers, the steel in the bridges that cross the rivers to enter the island and the subways underground whose rails create invisible barriers against the Fae. Additionally Soho was built as a safe haven from Fae in the 1870s with the cast iron facades that keep them from entering the buildings. This is all intentional as the NYPD has been waging a secret war on the Fae for nearly 70 years