Yeah, (yes), you are unfortunately, quite correct. The general education level for most persons appears to be dropping rapidly.
As a Canadian, born quite a while ago in the Imperial system times (feet & inches, punds and quarts), but raised in the Metric system (kilos and meters and Celcius temps etc.) I actually use both almost interchangeably. I am 5'11" tall, I ride 240 kmh, I walk 5kms to the store, dive to 130' max.....and on and on.
I find it amusing when my students are opening up the final exam book and I tell them that when they get to question 42, turn the page so as to get to the Imperial questions.
I inevitably get some curoius looks, so I explain they don't understand the metric system. I can see some disbelieving looks on their faces, so I ask them, okay, to the nearest inch, how many inches in a meter?
One out of ten can guess 39". So then I ask them, okay, let's have some fun, how many inches in a yard? Most can't answer, maybe 3 out of ten can say 36". Okay, how many feet in a yard? Blank stares. Okay, there's 12" in a foot. How many feet in a yard.
At this point, half of them are reaching for the iPods.....
Really? Can't divide 12 into 36 in your head?
I really have to wonder what type of education they have received and how prepared they really are for the real world.
Bottom line for all this?
Yeah, the books have to be written at a simple level. For Open Water students, why would any company want to scare them off with technical explanations?
Get them diving and give them the option to learn more indepth information when and if they want to.
I fly in planes all the time and have a pretty good grasp of how they work, but I know nothing of the true inner workings or operations of a plane. Don't need to. If I wanted to be a pilot or mechanic maybe....but just to come along for the ride? Where's the door, where's my seat, where's my food?
Idiocracy the movie: it's here. What are the most popular TV shows? The ironically named 'reality shows', usually with obviously contrived and over acted imbecile content. Find Brasil or Vietnam on a map? You must be joking. Who was president before Bill Clinton? Who fought on what side in WW2? Go into any typical new divers classroom and ask the students these kinds of questions.
I'm semi-retired, but I occasionally teach freshman writing to college students. Most full time faculty, my erstwhile colleagues, are happy to let me pick up a section or two, just to avoid the pain and maintain their illusions a bit longer.