For many web pages, responsiveness is not desired. For pages with lots of tabular data, for example, using fixed-width content areas is not only desirable but necessary. That is, responsive design is not going to eliminate the need for fixed-width pages.

Look at this page on your mobile device and do a bit of zooming, and you will see that the 100% header/footer stripes do not line up properly with this fixed width-content area. This page does not use the viewport meta tag, so the mobile device is choosing a default viewport width that the 100% header/footer stripes conform to that's different from the fixed-width of this block.