(Let’s say) Xavier is a big fan of ebooks and will use them over hardcopy books whenever he can.

Sometimes he has to give up on the ebook and get the hardcopy version anyway. This happens with some mathematical textbooks. The formulas show as very tiny and Xavier can’t see what they’re supposed to represent.

In some cases, he can use his app to zoom on the formula. In other cases, the app just won’t do it. In these cases, Xavier grumbles and gets the hardcopy.

My guess is that the publishers are just lazy. It is faster and easier to just use a graphic that was used for the original hardcopy and call it good.

If they’d cared, they’d use a form of graphic that drew the formula instead of using a pixel by pixel copy.

I’m also guessing that the author is too busy jumping up and down shouting “Woohoo! I got published!” To demand that the best graphical formats are used.