I'll give you a minute, and talk about the 800 lb gorilla for a minute. PADI claims that they are the way the world learns to dive, and they have a right to make that claim. I don't know what the percentage is, but at one point, more folks were certified PADI than all other agencies combined.
I have heard it is 3 X all other agencies combined.
As far as required reading? No. I don't think you can reasonably expect to "force" people to read more than the requirements.
It really is a case of: "You can lead a horse to water..."
We have seen thread after thread, bemoaning ther state of newly certified divers.
Every time I read one of those threads, I am always thinking, does anyone hold the diver responsible?
Whatever agency is doing the training, they can only do so much. Are there bad instructors? Of course there are, just like in any profession.
But in my mind, every individual that decides to take up diving, or any activity, is responsible for their own progression and skills.
Individuals either care, or they don't.
If they care, and want to be a good/safe/responsible diver, there are plenty of resources.
I found ScubaBoard very shortly after certification and I am pretty regular about coming here. I also found many great demonstration video's on youtube and other places using google or whatever that have helped me to improve.
I am under the impression that most new divers don't seek this stuff out. In that regard, I do like the suggestion I saw that the instructor handed out a sheet with different scuba related places they could check out. Even then, the majority would probably just toss it out anyways.