Why is book marketing/ promotions essential for authors?

Assume you’re watching TV and an advertisement for a new movie shows up. These advertisements have a fantastic title and a fantastic graphic. However, the only details are the title and the photo. These details give you no clue about the story or who the characters in the movie are. So does it make any sense?
Now tell me would you feel like watching this movie? Would you be interested in learning more about the film’s plot?

A teaser or poster aims at getting a general idea of what the book/movie is. But that isn’t all. Teasers, trailers, dialogues, songs, and physically going to numerous places are different ways for promotion. If promoting the movie is not done effectively, then it doesn’t reach viewers. Eventually ends up making fewer people watch it on the release day.

Now think of this same example differently.

Consider your book being released in a week. And 2/3 days before the release, you post the book cover with a line saying your book is releasing soon. Will readers read it? Would they be interested to know more about the book?

The purpose of advertising is to understand the product. And in your case, it’s the book. You would never buy something just by seeing it once. You trust it when you get to know more about it.
Ever brought Cadbury Celebrations during festivals or happy occasions? Why do your hands reach straightaway to Cadbury?
It’s because of its promotional ways.

Promotion is the king of getting sales, leads. Promotion is like chocolate to the kid who doesn’t know you. It is the source of knowing you and your product more. It is the trust you build about your product.

The book and the content(story) are of supreme importance, but marketing a book is also a much-needed part of releasing a book.

What do you think about this? Is book marketing important?