From a perspective of many years in and around the business:
Diving Dropout has always been around. (I'm looking at the 97% of US/Can divers being certified anywhere away from South Florida or good access to fair diving year round)
In the 1960's thru 1972, I didn't see it much happening. LDS parking lots were filled with Joe Six Pack vehicles, a lot of pick-up trucks with tools. A lot of lake diving, an occasional trip to some exotic place like Cayman with the local gang.
In about 1975 or so, I saw the arrival of the marketing that led couples to dive together for their big Honeymoon vacation. This was the beginning of the Diver Dropout trend as dive shops began to buy tables at bridal shows with travel agents.
One big "together" experience, all the shiny equipment, the excitement of conquering and cooperating. Done, now it's time to buy a house and concentrate on perpetuation of the species.
These two above situations are the majority root cause for the invention of Craig's List. (After E-Bay failed to deliver the insane asking prices for the out-of-hydro tanks and the snorkels with the ping-pong ball in the top)
The economic realities of the world have changed, insidiously, slowly, then in a flash. In the first 1970's period, at first there was very little competition for that "equipment intensive/carbon footprint" way to piss away our disposable income.
The biggest competition for your vacation dollar came from skiing, mostly on snow but to a growing measure: water sports toys, water skiing and PWC. The girls liked it better, it was less hassle, you could plan by weather forecast for "the next day", and the girls looked better​ in their bathing suits versus wetsuits. Plain sexist fact.
There was only Pabst Blue Ribbon, everything changed.
Tennis, Motorcycles, BMW Cars, Sporting Clays Shotguns, $1000 wristwatches, Import Beer, Designer Handbags, Outlet Malls, $550 baby carriages, Private Grade Schools, Apple everything, Viagra, Cable TV, Bandwidth, flavored f'ing Vodka. Don't ge me started on Golf.
DEMA went from an alliance, always very shaky in that regard, to an annual party. We, as end user consumers see the issues in SCUBA Marketing very very differently than the poor schlepps (that is the universal language of Manufacturer's Representatives that use this and other Yiddish words to self-describe themselves). The Manufacturer's Reps are looking for a revenue stream to make their roles viable, no less so than the "need" for manufacturer's to buy space at the (local consumer) Dive Show. When the LDS finally croak out, you'll see a door open on that retail dive-show "showroom" level for the manufacturers again.
Diver Dropout comes also from the fast dwindling numbers of Local Dive Shops. They long ago lost their appeal as hang-out spots, economics hit hard, a cadre of "dive club" members might have extended the gasping for air. And speaking of AIR, when the LDS closes down, where you going to take those LIME GREEN Luxfer 80's in the dusty closet to get them filled? Ahh, screw it, they might be 12 years out of hydro, but they'll go for a bundle on Craigs List...I'll throw in the spear gun and the booties, too.
Bashing Agencies? Really? I have had creds from 4 of them. They're all selling the same hamburgers. PADI is the easiest target. They own the hamburger stand market. If someone else wants to eek out a living from the leftovers, there only remains a coupe of ways to do it. Blaming any Agency for Diver Fallout is not seeing the bigger socio-economic picture of the much-sought-after leisure dollar. An Agency must provide the infrastructure for it to stay viable economically, and the same goes for it's instructor cadre- whatever level of financial success they want/hope/can achieve... If you can't/won't afford a McDonalds franchise, maybe buy the lot down the street, away from the corner, and start making gourmet burgers. Each and every Agency is in the Capitalistic Growth Model, whether the acolytes, their subservient priesthood is so motivated, or has lessened their goals, it is an individual decision. (Note to instructor- Step #2 is training for nitrox, EAN, whatever you call it and imbue the required use of same on every dive thereby boosting your profit margins on the service end)...but I, as usual, digress.
But, nevertheless, I can not resist . McDonalds Franchise costs me huge up-front, and I have to pay the toll for every burger sold, but I'm going to sell a lot of burgers. Burger King is a cheaper buy-in, I'll sell less burgers, but the corporation hits me for a lower percentage. Hmm. Now, tell me about What-A-Burger.
Further clouding the waters of the Agency responsibility in Diver Dropout springs from the prior paragraph, but how the process appears to the adherents, students and instructors alike. Once you get past The Big 4 (NAUI, SSI, and SDI are no different than PADI) the divers and instructors that are attracted then (after and following) to more Scientology based groups? They're not leaving. Masters of DIVER RETENTION. Feel free, as most do, to fill in the blanks as to why. It is the difference between buying a Formula Race Car and adjusting it over time for competition, versus buying a Dodge Hellcat and trying to figure out how to drive it. Either automotive analogy can be applied to either group of Agencies... depends on how you squint your eyes.
The party, at least the one we knew it to be, is over.
Yet, manufacturers of dive gear still crank-out this new year's model of the Titanium shiny object. You can still buy a Remington 870 Shotgun for $239 (by industry comparison, a paltry sum), but the dive industry hardware people can't quite figure it out.