I want to cite 3 other reasons why your main keyword is so important.
1. It will be included in your Title and h1 tag (content title) . These elements are the first read. It is during this fraction of a second that you can hook the reader.
2. Researching your keyword will help you in writing your article . When you have chosen your primary term, you will find secondary expressions. They will enrich your content. You can use them in your subtitles and thus have an additional boost for your visibility in search engines.
Studying the keywords your clients are searching for will make you a better web copywriter . This will allow you to enter the minds of your audience. You will understand the information they are looking for, the issues that concern them, how they talk about your services ...