2. As of April 21st 2015 your Google ranking depends on responsive design.

This was the day when Google said it would begin to favour mobile-friendly, responsively designed websites over non-responsive, non-mobile friendly websites.
And herein lies probably the most important reason for your business having a responsively designed website – your Google ranking and organically sourced traffic.
The number of mobile-friendly sites amongst the top 10-20 search results (page 1 and page 2 of Google) is steadily increasing as Google “tweaks” their search algorithm to favour responsively designed websites. As increasingly people search for your products and services “on the move” optimising your site for different devices is becoming more and more critical.