It's well known that most readers only want to "scan" pages so the can find the information they need quickly.

If readers can't scan your content easily, they WILL leave your site.

People landing on your site and quickly leaving is terrible for your SEO. It gives your site a high bounce rate and you'll begin to lose any rankings you had.

Highlighting text in your posts or pages is a great way to guide your reader's to the important parts of your content. Do this right, and you'll increase engagement and conversions.