With so many devices having different screen sizes,It's extremely difficult for a website designer to create many different layouts for each device. Responsive design solves this conundrum by automatically responding to its user's changing platform or environment such as screen size, orientation etc.

Some of the key advantages of a Responsive website are as follows:
1. It gives a pleasant viewing experience to users, hence increasing the number of returning visitors that also means increased sales
2. It is easier to manage and publish content at once rather than doing it for 4 different websites meant for various devices
3. Tailors the User Interaction dependant on the device they are on,leading to increased user ability/conversion rates

Its extremely difficult for a website designer to create many different layouts for each device.