There are tiling solutions for most OSes, but unless you can get access to an API as low level as X, they tend to not be as good. Amethyst is admirable in many ways, but it's a far cry from i3. Amethyst also has to wrangle with issues such as certain windows just flat out ignoring it, which i3 -- due to how X works -- doesn't have to worry about. i3 is a rock solid tiling solution that pretty much 100% works, and Amethyst is unfortunately a patch on top of another window manager and so can often be clunky.