People think writing a book is an easy job but its not. It is one of the most difficult things to do. You might have good writing skills but that doesn’t make you a writer. One cannot tell someone with good writing skills “hey, you have great writing skills. Why don’t you write a book?” And of course the book they want you to write will not be something that is of interest to you or something about which you know.
The first rule of writing a book is always write something you know about. If you don’t know or understand what you are writing, how would you expect your readers to understand or be interested in your book? Why is it so difficult for people to understand such a simple thing?