Not all Master Scuba Diver certifications/courses are created equal as stated above.
Deep Water Scuba, Scuba Navigation, Scuba Night Diving, Search and Recovery and Underwater Mapping - NASE Worldwide
NASE's MSD includes academics covering: Dive science, dive physiology, environment, scuba equipment, dive planning including gas consumption and management. Open Water Training includes minimum 8 dives, minimum 240 mins bottom time in: Deep, Navigation, Search & Recovery, Night/Limited Viz, Mapping, and Digital Imaging. I add Wreck Diving requiring use of reels.
This NASE MSD is a pre-requisite to Divemaster. For the same reason as stated in post #10, many go into DM courses to get the knowledge & skills but don't really want to be insured dive leaders yet. NASE has broken out the knowledge and skills so that DM training focuses on leadership and professionalism.