Remember the HTML `` element? It’s deprecated, so it’s not like you’re going to use it when you need some sort of horizontal auto-scrolling feature. That’s where CSS comes in because it has all the tools we need to pull it off. Silvestar Bistrović demonstrates a technique that makes it possible with...
Why in the world was marquee removed? It probably does a better job at scrolling than CSS. Look at everything that had to be written just to mimic a fraction of its power!
To make it efficient, you'd also have to add and remove elements out of sight to save memory. Pure CSS doesn't do that.