People used to make only desktop versions of the site. They never thought that they will need to make mobile version of the site. Responsive design is nothing but your website fits to screen of any size, it can be 18 inch, 21 inch, 32 inch, 40 inch. You don’t need to create mobile version of the site. It automatically fits to smartphones. In today’s online world every site at least take 10% of the visitors through mobile devices. These visitors are always provide better conversion than desktop users. If your site is not responsive then you site wouldn’t be mobile friendly site that will lead to less number of conversions and high bounce rate.