Teri, I'm not getting a sense of "why" as in, why you think authors shouldn't be doing it?
Like Amarie said, in the good olden days it was unnecessary because of the pubhouse machine. Now, pub houses leave authors to fend for themselves.
Of course, there is a difference between "good" promotion and "bad" promotion, but in today's industry, "no" promotion is suicide.
I don't have time to edit, so this will be long!
Well, in my case promoting wouldn't have made any difference. My book was printed in hardcover. Within 6 months I earned out the advance. Eventually the print run ran out and it wasn't reprinted. Would it have been reprinted if it had sold out faster? I don't think so. I don't think Cricket reprinted books after the first run. What they did is the books which won awards they sold the paperback rights. My book didn't win any awards, so the paper back rights didn't sell. Promotion wouldn't have made any difference.
With ebooks, it seems to me even less important to promote because the books don't go out of print.
Also, readers can sample the first 20 percent to see if they want to keep reading.
The sales you get from telling people are really small and won't make much difference. What you need (it seems to me) is for readers to find it, like it, and tell other people.
How will they find it if nobody knows about it? Well, all I can say is they do. I know this from the books I've self-published. It's weird that people find it.
Word of mouth cannot start from friends and family or online friends. It has to be genuine and spontaneous: WOW I just read a great book, sort of things from one friend to another, not connected to the author.
Maybe what I don't like is bad promotion. I like to think that a lot of what passes for promotion is pointless because readers are not fooled.
For example, I think only authors care about Amazon rankings. I think readers who don't personally know authors don't pay attention to it, and have no idea what it means. But authors obsess and do things to elevate the ranking. The moment they stop, the ranking goes back down. To me this is a waste of time. Write your next book and forget about it.
Came back to highlight. Still no time to edit but this is the important part of the rambling:
Also, here's what I learned. Having published a novel already from a respectable press definitely gets my queries read more carefully with my next books. But when I sold TS, nobody cared the slightest how many copies RW sold. Nobody asked anything about it. All they cared about was whether they like TS.
The way to earn money as a writer is to have more books out there, not squeeze sales of out of the first book.
Again, wrote quickly, so this is probably too long and sloppy.