In their searches, Google ranks businesses with a fully-optimized mobile platform higher than ones without a mobile platform, making it imperative for all companies to be up to date on all devices.
Different devices mean different customer needs. When visitors land on your site via mobile or tablet, they don't necessarily need all of the information that's on your desktop site. Too much content slows down a phone so only show what's really important to a mobile user.
Studies show that 75% of web users admit to making judgments about the credibility of a company based solely on the design of its website while 73% of visitor's prefer a site that is optimized for mobile.