Approximately 55% of web users access websites on mobile devices, and the figure creeps steadily higher. This is why you should be using a responsive theme for your website. This article explains all.

Beginning April 21, Google will use mobile-friendliness as a ranking signal in search results, rewarding websites that are fully optimized for mobile platforms. Most modifications to the all-important Google Search Algorithm have only a low-weight impact on search results, however Google says the effect of this change will be profound. It is very important for any business owner with a website to respond accordingly. Effective immediately, Google will also factor content from mobile apps (a feature called App Indexing) when rendering mobile search results. Android users who are signed into their Google account will begin to see apps more prominently in search listings.

Source: Now Is The Time For Responsive Design – Forbes