"On the other hand, if you had that much power, why waste your time building your own materials when you could just as easily use someone else's? It's much quicker to contract someone for the lumber than to chop down a tree yourself."

Strange doesn't know if Lilith could actually build people up from scratch. But in his mind, if she wants to use people for...some reason, then there's a whole multiverse full of them ripe for the taking. Which is a bit morbid, but there you go.