Every single visual experience that has a bounding plane has to deal with aspect ratios, whether that's a photo through a 1:1 ratio medium format camera or a 16:9 ratio 4k movie. If there's a visual bounding box around the scene then everything in the scene must deal with the ratio of the width to the height.

CSS is one of the only visual systems that has no concept of aspect ratios despite the performance benefits of knowing the aspect of a block before the contents of the block are available. If you know the aspect ratio of a block, and you know the width of the page, then you can render the block immediately because you only need one dimension to render both.