In defense of the kit creators, I actually think it makes sense for them to provide highly simplified instructions. It is pretty bad that they tell people the beer will be done so quickly, but outside of that, I think it's fine that they leave out so much other info.
Different people learn in different ways. Me, I like to learn as much as I can about a subject before I dive into doing it myself. The best way to do that is by reading a book. Myself, I started brewing by reading Complete Joy Of Homebrewing. After three moderately successful batches using purely info from that book, I found myself with questions that it didn't answer, so I got a couple more books, and found these forums. Having these extra sources of info helped me figure out which things in Papazian's book are universally true, which are personal preference, and which are outdated and have since been improved on. But that book did a great job of getting me started.
Other people prefer to learn by doing rather than reading. My girlfriend, for instance, would never have made it through an entire book before her first brew. Give her a bullet list of ten steps, and she'll follow them. Then maybe next time around you can add a couple of extra steps, as she gets a better handle on what she's doing. But give her a list of fifty steps, and she'll give up in disgust, or randomly decide to skip half of them.
So what is a brewing kit creator to do? Sure, they could make instructions that talk about water chemistry, aeration, oxidization, pitching rates, etc. But many first time brewers will never bother to read so much info. Of those who do, I bet a high percentage would find it absolutely terrifying, and end up on here posting "did I ruin my beer by adding half a pound of salt in an attempt to fix my tap water?" threads
And for the handful of people who really do want so much detailed info before they attempt their first brew, surely kit instructions are the wrong place for that in any case? At some point, the instructions get so complex that they'd be better off just selling a book along with the kit instead (which was exactly what my LHBS did, bless them).
I don't think the goal of kit instructions for a first time brewer is to make the best beer possible. It should be designed to make beer, ideally decent beer, but really any drinkable beer is good enough, in as simple a way as possible, without introducing anything scary or complicated or that requires too much in the way of precise measurement or process control.
The sad thing for me is when I see people who have made dozens of batches, but are still using simple kit instructions, pre-hopped extract, etc. That's fine for your first attempt, but somewhere around batch two or three you really need to learn more than can be fit onto a single sheet of A4 paper!