Rectangles with rounded corners are mathematically wrong. Once you know why, you can’t unsee it. Squircles, made iconic by Apple, are finally supported in browsers by the new CSS corner-shape: squircle property. I will show you how to approximate one squircle corner with just three pixel-perfect Bézier curves, so you can use squircles everywhere: canvas, SVG, clip-path, and even game engines. Your eyes deserve curves that actually make sense.
Market share has nothing to do with whether you should care or not. The author also says to care about other chromium browsers, which have the same minuscule share as ff