Is Responsive Design just a marketing buzzword? No, Responsive Design is a leap forward in the web design industry that effects both designing and developing for the web.
The constantly rising popularity of smart devices (tablets, phones etc.) has created a serious demand for websites that are viewable on small displays.
A 2012 TechCrunch Survey predicted that by 2013, mobile devices would overtake desktop PCs as the dominant global Internet platform, with a projected 1.9 billion users on mobile devices in 2015, compared to “only” 1.6 billion desktop internet users. So why haven’t you started creating responsive websites yet?
Even Google recommends responsive web design:
Google recommends webmasters follow the industry best practice of using responsive web design, namely serving the same HTML for all devices and using only CSS Media Queries to decide the rendering on each device.
Source: Google Developers