User Experience - By optimizing the mobile site will lead to an increase in the overall user experience.
Faster Load Time - Faster load time for websites will impress your customers. As well as they spend more time than the normal websites. It will also lower your bounce rate of the website.
Higher Ranking - By optimizing the mobile site will lead to a higher ranking in search engine results pages. This increase will give you more traffic on your website and increase user spam time also.