When beginners strip, break, damage, and lose parts and will not even buy a shop manual. Many of those parts are no longer manufactured.
A real shop manual... not online down loads.
You mean a real paper copy? I downloaded the pdf of a few different bikes and then printed them out and put them into a binder. I don't know if that counts or not. Honestly, for the most part I only need select information. In fact, I could probably just make a "cheat sheet" for most of the stuff. I was able to restore my 77 550 by using a pdf. The only real info I needed was clearance info, and torque specs. I had to re-do my pd carbs without anything because I couldn't find a great exploded view. I got through it. If you have a general idea of how things work, aside from torque specs I don't see the complete need for a manual. Obviously it will help. Back, before the internet it was probably a lot more difficult to get a manual for an older bike. I agree though, if you are a complete beginner do like I did to learn, lable everything, put all your nuts and bolts into dividers so you know where they go and make sure you torque everything with a decent wrench, not some harbor freight deal that may be off 10ft/lbs. Let's not forget Lucky that we cant fix stupid. Even a manual wont help that. 
A PDF is a (portable document file) developed by large businesses to transmit large documents over the web at high speed.
Of course there are 3 levels of PDF's with different quality.
Web quality,Print quality etc.,,
It takes a special program to change the quality of the PDF.
You cannot easily alter a PDF file with out all of the add on programs like(Pit Stop) etc.,.
You have to buy each one of those programs.
Some PDF's have security codes and can even open with a music file.
If you save a Photoshop file or illustrator or Freehand file as a PDF, then you will not be able to alter that file.
Artists do not like PDF's. IT will take a Photoshop file or vector file which could have 44 editable layers, and change it to 1 layer which then cannot be altered.
Business people like them because they do not know about Photoshop or vector based programs.
I don't think people are stupid, I think they just do not have any interest in details.
They just want to use things and do not want to repair them.
A young man learns hopefully that if he breaks his bike, he will have to fix it.
Some dads just bought the kid a new bike instead of showing them how to fix the bike. So the kid learned that if something does not work or breaks, you just buy a new one.