I feel that as your snake gets more comfortable with you, it thinks of you not as a threat anymore, but as a life source. They can't eat, they can't drink, they can't live without you, and I think they seem to get that after awhile. I don't know, maybe I am crazy. just my opinion. I have seen the nuxzling a little bit though, my ball seems to like going through my hair, and curling up on my shoulders, but could just be forbheat. I like to think it is affection though