My pdoc, who I've seen for years, used to do this. I usually attributed to mood since it didn't usually reflect the tone of our sessions. I still felt alternately hurt or awkward since it does feel odd and it bothers me to leave any meeting without some kind of closure. I eventually made a point of saying goodbye after each session if he didn't first. Sometimes I said it casually and sometimes it was with a little sarcasm. It isn't you at all- it's always the other person in this kind of thing. I think some people get absorbed in their own stuff or are just moody and don't realize it. Now there's always some kind of good-bye at the end of session.