Improving user experience is the key concept around which SEO best practices revolve. An impressive content and well optimized page is a perfect recipe to rank on the top of the search results.
And writing clear, descriptive and engaging Headings comes as the first step towards improving user experience. Headings improve the visibility and readability of the content piece and helps in engaging the user.
Optimized Headings are an important ranking signal for Google and helps in setting the relevance of the page wrt the user search query.