As a professional photographer, I almost always retain the copyrights for my work. I need my clients to come back to me for prints in order to make enough money to get by. If I was only charging for the photo session and not the prints, I'd have to charge a much higher price, which would scare off too many people. So it's not just an issue of promotional materials, nor is it one of greed. It's about keeping the photo session at a reasonable cost so that the client can the decide how much money the want to spend on prints. Also, when I client orders a print from me, I spend time "cleaning up" the photo (I work all digital), and making sure that the color, brightness, etc are perfect. The cost of the print pays for my time, and I believe that my clients are getting better photos that way.