If you think you never have, you're likely wrong.
A lot of work that is published has been written by ghostwriters. Why wouldn't you know that?
Well. . . because a ghost stays hidden in the background. The Author is the Author of the work. The ghost unlocks the power of their ideas and writes in the Author's voice helping the Author to shape their ideas and get their work to market more quickly. The Author owns the work and gets to decide whether or not the ghost should be acknowledged. If the Ghost is interested in being acknowledged they will discuss and negotiate the terms of disclosure.