It's just so easy. It's probably harder to not do it.
Audio has been around since, I suppose, the spoken language. The difference now is distribution and availability. Audiobooks, podcasts, smart phones, voice controlled home...
Gone are the days when a publisher could take out an ad, count on a few reviews, and have an author do a couple...
My only concern with using dictation is how my mind, and how my imagination, will adjust to it.