My indie-released songwriter friends never understood why writers are so hung up about self-publishing. Or the more recent hybrid version, where a publishing house helps you create the book and you fund it. Musicians have long separated from the labels and ventured out on their own, releasing their own CDs and working with indie distributors.
Even today, writers are told that unless we get an agent and go the traditional route, we'll never be taken seriously. We'll never make it as a writer, whatever that means.
I've played both sides of the court. For years, I went the traditional route--agent, large publisher, small press, radio and TV marketing paid for by my publicity budget with the publisher, even book tours back in the day. I also have self-published twice, creating a professional book with hired help (typesetter, cover designer) and promotion.