For me this whole thing comes around the progression from dependance through independence to interdependence
. There are people who are quite content in each of these modes of relating to others.
My preferred mode is interdependence, where I can have a select few people on whom I know I can rely - they've "got my back", as it were. I don't care whether they live with me (primaries) or don't (secondaries) - I can still form attachments and I enjoy those attachments - I just don't give them out willy-nilly. It takes time to develop a foundation of trust that allows for a solid interdependent relationship to develop.