I look back at my initial open water course. That was 15 years ago (was 37 at the time) and I threw around 40-60 lb boxes all day long for a living, I wasn't in that bad of shape at the time. I came out to Kona and took the course, the instructor did a fairly lame and quick job of it, but by golly, at the end of the second day of dives after lunch and a beer.... I wasn't sure if I could make the dives I'd scheduled the next day. I was tired. I only got about two hours of total bottom time over two days (I really sucked down the air to start) and I was wiped out (sun could've been a big part of that). I ended up making the dives the next day after a good night's sleep and loved it. Afterwards I went home to Oregon and took the entire course over with the local YMCA guy and eventually got to instructor level before moving out here.
I try to remember personally how tiring those first diving experiences in Kona and Oregon were, and think of how many of my students over the years that likely couldn't handle a 4 dive day (sure several could, but I'm not sure if the bulk could) no matter how long the dives were, and I just can't see it as a positive thing in most situations. Unfortunately, if we could offer the one day checkout dive scenario, LOTS of divers would sign up... then LOTS of divers would be disappointed in not finishing in the allotted day. I see trying to make diving as an inclusive hobby/sport that can accommodate people of most all physical skill levels as being a good thing for the industry. From what I've seen over the years, given the choice, most people will take what sounds to be the easiest way. What often sounds like the easiest way doesn't always turn out to be the case, and it's potentially stressful. Lots of people tend to handle stress by quitting, rather than scheduling an extra day, then badmouthing whatever or whoever they've just quit. I'd suspect we'd see a lot more of that if the one day checkout dive option became a routine thing.
On the customer satisfaction thing... PADI supposedly sends out a certain portion of all students a survey shortly after the course, wouldn't surprise me if the other agencies do as well. I've gotten a couple "attaboys" over the years from people who've filled them out, but I suspect most go straight into the recycling pile/waste bin at customers home. The one year followup would be a great idea, but I suspect the people who are filling out the initial surveys are likely to be the divers who are more engaged to the hobby, and would be the same one's filling out the later ones and it'd be skewed enough that it wouldn't paint an accurate picture.
I personally don't think changing the length of the course by a day would really affect the number of divers out there. There are much bigger issues with the industry. Unfortunately, these days you just don't have as many local mom and pop shops teaching divers as you did a few decades (even years or months) back, and sadly it probably will get worse. The local stores and instuctors that were the backbone of the sport/hobby (in my mind anyways) are becoming more rare.
