Why? I guess I liken it to wanting to have a photo of anyone I had been close to, kind of like a memento of our time together, and the experiences we had shared. Like a friend, a lover, a co-worker, a special babysitter, etc. Heck, I just finished my divorce (went to court 3 days ago and made it final!), and I felt my lawyer and I had been through so much together, that I wished I had a picture of her. I don't think it's unhealthy, just human.