I keep seeing references to guys go fast and women go slow. In my experience with insta-buddies, the newer the diver the faster they go. I've had plenty of women buddies that are olympic racers. With more experience you come to learn (with certain exceptions) that this 100 ft. of reef looks alot like the next 100 ft and if you'll stay still, stuff will come to you. I think excessive finnning for new divers helps with their bouyancy and trim. It takes practice to be still and hover. I've seen really experienced divers take a nap.
Not just newer divers, but also experienced divemasters/guides who race along the reef, possibly in the belief that the divers they are leading will feel cheated if the guide doesn't take them on a "journey."