The whole goal is UX deisgn and tryng to make the consumer feel as though their experience with your product, material, and site are worth their time. Otherwise, why would someone persuse a site just to simply get frustrated with the User experience and content? Simply put, they wouldn't.Although U/X design is a seperate catagory of design and coding-- something typically reserved for more advanced designers or those who have apecialty training, responsive web design as a whole is a necessary skill to have as a web designer or coder to help improve and facilitate ease of use and vision with your work.

Responsive Web Design

User experience and the mechanics behind it.