An on-page SEO helps search engine to identify and read the content (as per Google’s algorithm) and relate the content to the query raised by the search intent of the user. To help google understand the content it has to be optimized to the latest practices understood by the search engines. This also helps in better ROI.
More than 50% of the web traffic comes from Google and Bing. Designing your website to be search friendly is essential to rank your page on search engine