Writers, Do You Know Why Your Books Aren’t Selling?

I did a mini-focus group on why writers do not know why their books are not selling.

You’ve poured months—maybe years—into your book. You crafted each sentence with care, fought through self-doubt, celebrated when you wrote "The End." And yet… sales are barely trickling in.
You wonder: Why isn’t it selling? Is it the market? Is it me? Is it just bad luck?