Most people don't read manuals. Or if they do, it's only a small part of it, ususally just enough to get them into further trouble.
The paper manuals that are left are incredibly bad, very little real information. By that I mean info that someone who has two geek brain cells can use. On the other hand, most pdf's don't have that kind of info, either.
The cost of producing millions (after all, software is now sold in the millions) would be prohibitive. I remmeber my dBaseIV package: six floppies and three very thick three ring binders and about five softbound books. It must have weighed over ten pounds! That, and the relatively low volume sold, is what made it cost $400.... fifteen years ago.
If one software company puts their manual on a @#$!! pdf then everyone in the same genre has to, also, because of cost and competition. Oh, well....
Like it or not, and I really don't, pdf or some variant of that is going to stay here. (It sure is hard taking a monitor to bed to read.)