1. They need writers because they usually can't write the material themselves. Some people hire ghostwriters because they don't have the self-discipline to sit in front of a screen for hours at a time.
2. It's also easier for someone else to write an autobiography because they can write more objectively. The authors are sometimes too close to the subject or may want to include something important to them but not of interest to readers.
3. A few people have approached me to write for them because they are public speakers and they want books to sell at the back of the room. They know their gift is oral presentation; they know they don't have the skills for writing.
That makes sense. Once they've spoken (if they're good), people want to buy their CDs and their books—especially the books.
People need ghostwriters for good reasons.
I want to help them realize their desire for a book.