I guess I might take this as a red flag. If I really liked the publisher for other reasons, and if they had good bookstore distribution (the most important question for my category), I might struggle and come up with a list of some basic stuff I could do to promote the book: organize bookstore readings, social media stuff, create a mailing list, apply to book festivals, pitch reviewers, etc.
But all of that pales in comparison to what a real sales/ marketing department can do for a book. I went to a convention where salespeople from my publisher were going around and pitching my book and other titles to individual booksellers. They put the book on Netgalley, they sent out ARCs, they sold copies to schools and libraries, and probably many more things I don’t know about. There are very few of these things I can do myself.
So, I guess I can see why publishers (and now apparently agents) would want to know writers are ready and willing to promote. If it’s a kind of test, a hoop to jump through, I don’t love that, but okay. But if they really think a writer alone (who doesn’t already have a big social media platform) can turn a book into a good seller ... well, I’d rather self-publish than go with a publisher who has expectations I personally can’t fulfill. (I don’t feel the promotion I’ve done has been very effective, though I put a fair bit of time and some money into it. And, let me add, I wasn’t asked to do any of it. It was my choice.) At least if I’m self-publishing, I can control the price and all the risk is on my head.