The printed book for many is more about packaging than content. Younger people in particular are choosing digital whenever possible because they’re more interested in having immediate access to the content than how it’s packaged. A big heavy book is less attractive than having the info on the device they’re always on — their phone and tablet.
Not only do their laptops not come with any DVD or CD player, an increasingly large percentage of them are just ditching having a computer at all. Phone/tablet, that’s it.