Within the modern era of the internet and social media, the new standard of writing books: Self-Publishing, has forced authors to develop business skills. They are now responsible for marketing and sales of their product. These efforts are not just for the books they write, but the writers themselves.
Fortunately for me, I have started and developed small businesses first, before getting into authorship. The downside is, I spend more time working on the business side of book writing than the writing itself, and worse less time on the research needed, to begin writing.