In construction trades a Master is rarely conferred on anyone with less than 10 years experience and demonstrable mastery.
They are also normally able to teach, so maybe instructors would better be suited for the title and we call all use baiter or equivalent for novices with a couple of hours underwater.
The problem is they want to reach and inspire newer divers to keep taking courses and expand their experience by offering something prestigious-sounding but realistically achievable in the intermediate term.
One of the problems in my view is that once people get AOW in the PADI system (which seems to be what most American divers come out of), and many want to 'up their game' in diving without going into technical diving (which they may not be ready for anyway), they're not sure what to do. I got the impression many consider or actually pursue Dive Master because they think it'll make them substantially better divers, rather than because they intend to act as dive guides or go on to teach or assist in teaching.
NAUI's Master Scuba Diver course was, IIRC from having it explained to me years ago, intended to impart instructor-level knowledge and capability minus the teaching aspect. That sounds a lot closer to the mark, but NAUI doesn't seem to have near the name recognition of PADI in American divers.
I imagine most divers who aren't on ScubaBoard don't know what GUE is, much less GUE Fundamentals, and GUE's gear requirements would be off-putting (like telling divers that BCD they paid a lot for at their dive shop was a bad choice, ditch that think for a BP/W).
I'm okay with things as they are. If someone wanted to offer a revamped Master Scuba Diver course offering customers what they wanted, with more credibility, I suggest:
1.) Peak Performance Buoyancy as a required course, since this is expected to be honed in an excellent diver. Also include some alternative kicking styles - such as frog kicking.
2.) Underwater Navigator, as one would expect a 'master diver' to have at least some basic skill with it.
3.) Deep Diver - but augmented with a little deco. teaching? Not so much to encourage deco. diving as to accept divers who push the limits may go into deco. accidentally, or choose to to stretch a dive for an objective, and it'd be good to have some idea how to deal with that. Teach alternative air source options and do a dive with one.
4.) Solo Diver - seems like if you're a 'master,' you ought to have the knowledge and capability to conduct benign conditions dive within your experience level without relying on a buddy. I think with current standards this would boost the minimum dive count to 100 going into this part of the course, which may be too far out to appeal to some new divers.
5.) Some variety - not sure how to judge this; perhaps known experience in a variety of environments (e.g.: ocean, cold water (e.g.: California, deep quarry diving), drift diving, wreck penetration or cavern), etc...
I started to recommend wreck or cavern diving for penetration experience, but fear encouraging people to do penetration dives might lead to overconfidence and fatalities later.
What I struggle with is what the customer needs and wants. The NAUI Master Diver course manual has a lot of info. that's interesting if you're into theory, but I wonder how many customer's idea of a master scuba diver is one who has excellent horizontal trim and buoyancy control, can engage in tasks while maintaining those, a good gas consumption rate and navigates well (hardly giving a thought to gas laws)?
Alternative: If PADI came out with something along the lines of GUE Fundamentals without specific gear requirements, would that suffice? I've never taken that course and don't know the details on how it'd compare to what I described.