The smaller houses might not put the effort into the advanced publicity; some just don't have the resources. I used to handle pre-book publicity for two author friends. One was with Ivy/Random House, the other author with Adams Media. Neither author was A-list. Both wrote nonfiction, and always, it came down to a combination of efforts. I created the author presentation packets, actively sent out press releases, and provided ARCs to newspapers and magazines to fulfill review requests, keeping the agent, editors and publicity departments in the loop. Ivy put effort into other forms of promotion and did a tremendous job overall, but they could afford to.
Now that I'm my own marketing maven, it all seems like uncharted territory. Recently, I asked authors and readers within my circle if they could suggest an author to do a book blurb. I felt awkward contacting someone I hadn't met, so I approached two authors whose workshop I attended at a recent conference, and another author from a writing organization I also belong to. My publisher provided an unedited ARC for this purpose. I intend to seek out two more authors to make it an even five. If you don't have a publicist or agent to handle this for you, talk to your editor or the person in the publicity department overseeing your work, and be open to taking on this task yourself.