Looking at the traffic data for one of the websites that we oversee, we found these numbers for a recent random day:
9 visits from different people using Facebook on a desk top computer; versus
261 visits from different people using Facebook on a mobile device.
In other words, the number of unique visitors using a mobile environment was almost 30 times, or almost 3,000% percent, greater than the number of visitors using a traditional desktop computing experience. If your website is not mobile responsive, or mobile first, you could be missing out on an awful lot of business.