Making Google happy
It has always been important to make sure your website displays and functions correctly on mobile and tablet devices not least to ensure your users have an optimal browsing experience.
Since the 21st April 2015 Google actually announced that it would take in to account whether or not a site was mobile-friendly, which in turn would then have some bearing on where in the search results a site would appear for any given search term. If your site is not responsive then this could have a massive negative impact on your traffic.
Fundamental is mobile-friendly out of the box and will ensure you obtain the best search results possible in the search engines.