Talk to any serious author, and being an author involves so much more than marketing a book!
The role means you have to prioritize so that when you write, you write in peak times, when you have plenty of spark, and energy to put your all into the primary task - writing.
Of course, an important aspect of being an author is to meet your audience and readership, through booksignings, "appearances" on social media, such as Facebook, Twitter and LinkedIn. That is one way you can reach your fans.
However, not all social media sites offer the opportunity to engage in a deep way with people, and "impressions" you leave may be transient, and unsatisfying for both reader and writer.
This is why I take the time to write a blog - here on Goodreads, and, from time to time, elsewhere. It is my way of saying thanks to my audience, paying it forward, and giving them a taste of my writing. Readers can experience me and my writing first hand. It is my belief that good writing should speak for itself.