I think part of the reason people drop out of diving is because of lack of confidence. The push is to get students diving quickly and to quickly finish up their certification as soon as possible. In my opinion this produces divers that do not have the proper confidence needed to dive without their instructor to assist them. The other reason I see divers not continue to dive is because they never wanted to in the first place. For example a wife learning to dive because her husband dives. I personally have slowed down the class to ensure my students feel comfortable with and without me. We then created a "dive buddy" system where if solo divers booked a dive on our boat we would start calling our people from our "dive buddy" list. Most of the people on the list were members of past open water classes, by calling and inviting them to dive they had a tendency to say yes.