Static font sizes are great for most cases in responsive websites. In some situations though, you find yourself wishing that your typefaces were a little more adaptive than is achievable with simple 2 or 3 stage media queries
Simple autoscaling based on the width of a container such as a column does not work. In responsive sites columns will not fluidly change width. Instead they may jump to a new width at a breakpoint (such as for small screens) and then max-out once you get to the site width.