I thought is was so cool when I looked at these really sleek, beautiful web pages. When I would scale the page down in the browser, the images would scale also, proportionate the the resizing going on with the content in the page. Images scaling, background images scaling. This is what scaling images with CSS for Responsive Web Pages is all about.
I did it for my site, sillybilly.com. It was cool I thought. But then I went on to other clients and other projects. I walked away from the code for a couple of weeks. And then BAM,,,,, all of a sudden, it was everywhere and every client wanted it to happen, or to learn how to do it.
The more I worked with WordPress clients and thus the WordPress themes involved, understanding the concepts around scaling images with CSS for Responsive Web Pages became a must.