Why doesn't the iBooks for iOS App support a wishlist?

iBooks for iOS has been available for several years and I still need to add books to my Desktop iTunes wishlist. The iTunes Store App wishlist doesn't show books and the iBooks App doesn't show a wishlist on my iPad or iPhone which means I need to go to my Desktop system to look at my wishlist.

Apple products are supposed to be user friendly so come on Apple there must be a way of adding wishlist support for books to either one or both of these App's.

Frustrated!