I have to guess that maybe the illustrator didn't give them permision to include the artwork in an electronic edition.
We, as e-book builders, had and issue a year ago with a book we recovered from print and edited in digital. The artist was NOT happy with the idea of including the artwork. «Anyone can extract and manipulate the images.» he said
The same as it could happen with any font embedded...
Not everybody is ok with the "digital world".
And the issue with the images coded in the book, could be dued to editing in InDesign or similar. Instead of deleting the code, maybe, they just deleted the images from the folder...
Not a good practice but quick
I, personally, use ereaders mainly because of font-size. And I hate when the print edition is different from the paper book
