To edit it. MOBI ní ìṣàmúlò-ètò Kindle tí a tì fipa mú, tí AZW3 tí pàtó láti pàtó àwọn ààtò Kindle, which is optimised for reading rather than revising; a document format is what you need to make changes, add comments, run a word count or hand the manuscript to an editor.
Illustrations, diagrams and the cover are extracted and embedded in the DOC at their original resolution, positioned in the text where they occur. Formats that link rather than embed get the images written alongside.