We often talk about recruiting new divers. But I think we should primarily focus on keeping current divers, especially the new ones. @Beau Holden mentioned in a post above how dive shops in his area don't seem to cater to current divers. Same idea.
I suspect you then need to divide the direct sales industry into trainers and equipment sellers (e.g.: local dive shops) and trip providers (e.g.: day boats, liveaboards), because what profitability of a new diver and a retained diver vary markedly to these different classes.
I got certified in '06, and have been blessed with multiple dive trips and over 550 dives today. My last certification was SDI Solo Diver, back in 2012, IIRC, and I'm not interested in technical or professional courses. I live inland, and am slow to pick up motor skills, so GUE Fundies or similar isn't likely. A shop's not likely to sell me a course. I've got a full set of gear (and gear I don't use anymore). In a given year, I tend to hit the local dive quarry if I don't make it to the ocean...which hasn't happened in years.
I'm a retained diver, but few and sporadic air fills, tank hydro. and viz. services, the rare regulator servicing, and very occasionally a part of some sort (e.g.: BP/W sexbolts, a miflex hose) don't offer a lot of profit margin to a retailer.
We are currently running an InDepth/Scubanomics survey precisely on this, and the preliminary results are stunning. People do not feel ready to dive after receiving a c-card trumpeting they are.
Depending on how you define 'to dive,' they're not. Many people don't live near good ocean shore diving, and navigation and situation awareness diving can take a long time to build to good competence, if it ever happens. So if a similarly trained buddy pair diving alone from a boat without a guide is the standard of being ready to dive, I suspect a very small minority of fresh OW graduates are 'ready to dive.' At one of the more benign entry/exit Bonaire shore dive sites, they might be okay.
Experience counts for a lot. People spend a lot more time on the road before getting a driver's license than OW students spend diving, and driver's get on the road and stay in practice far more often than most new divers dive. I used to watch another diver assemble their gear and had trouble remembering which way to point the tank valve, not because I wasn't taught, but because so much time passed between doing it.
We need to move away from training agencies having such a dominant role in our industry. As Alex Brylske keeps on saying, we need a new paradigm with a focus on diving, not on selling courses.
Are the training agencies preventing someone/something else from doing something needful? If they don't have this dominant role, do you see someone else taking it, or no one?
What does this 'focus on diving' look like that's different from what we have now? PadiTravel, Liveaboard.com, Maduro, Aggressor Fleet and Explorer Ventures send me e-mails promoting dive trips. A number of groups in my region offer dive trips. There's a local dive quarry with an on-site shop.
My experience with retention is that the divers we've trained in NB/T have a ridiculously high retention rate. They also make more purchases of equipment.
Do your students tend to be the random public 'pool' providing most OW students nationally, or do you tend to draw a more select group somehow (e.g.: maybe you have a good rep. with area serious divers and they preferentially refer contacts to you)? Do your instructors do more active social engagement/mentoring with the students? When you say high retention rate, do you just mean they keep diving, or that they maintain active involvement with your shop, dive club, etc...?