There are many arguments in favor of including an ebook download with the physical book: it adds value to the physical book, it enables booksellers to sell digital books alongside print (and customers to buy ebooks in shops, where they discover them) and most importantly, it’s just downright convenient. Much like the music industry’s pairing of vinyl records with MP3 downloads, by bundling print and digital, publishers can meet readers’ demand to consume media in both digital and analog forms.

Source: Ghost in the Machine: Does Print+Ebook Bundling Have a Future?, Joy Hawley, August 26, 2013.