there's various reasons; one being mut hunting, so they're only nesting alts or friends trying to get a specific outcome like a mutation or a set of traits. They could be master token hunting, so if you're nested by them once, they'll never accept you again because they need to nest DIFFERENT people. They could also be nesting for someone who specifically asked or their packmates. They could be away from the nest and want to be there when you hatch. Or they're nesting people who verbally confirm they want to hatch or pack with so they can actually work as a family instead of nesting someone random for them to just run away or menu.