If you’re working with book-length material, editing becomes much different process. After a certain size, a manuscript acquires sentience. You may say, “I think I’ll add another illustration, here.”
The now-powerful manuscript will say, “OH, NO, YOU WON’T!”
I once wrote a book with numbered figures AND illustrations. And lists of both up front. Each picture required (a) the picture itself, with caption (b) a note in the text to tell the printer where it went, (c) a reference to the picture in the accompanying text (“As you can see in Figure 45…”), plus (d) an addition to the list, (e) renumbering the rest of the list, (f) renumbering all the captions after it, (g) renumbering all the following printer’s notes, (h) renumbering all the text references.
“Hey, you’re right. I think I don’t need another picture, after all.”