Things don't happen instantly. You could have doubted it was in Microsoft's interest to support Linux within Windows for years... until they released WSL.
Windows machines already support Linux on the hardware level. Getting an Intel or AMD CPU to virtualize a Linux kernel is simple. Worst case scenario is an Nvidia GPU, but since you only need the compute drivers in WSL you avoid Nvidia's graphical issues. There isn't any work required since the OEMs already did it, the only thing required is Hyper-V.
Apple is selling a custom CPU core that has no driver support for anything but XNU with a BSD userland. It doesn't support UEFI, it depends on Devicetree bindings and would demand constant updating and support to render a "first class" Linux experience. Once again, anyone with a protracted interest in staying supported by upstream Linux should not be using a Mac and praying the community cares enough to make it good. Apple knows it's a novelty, and they're not going to take it seriously because that's just what they do. MacOS and the App Store is profitable, Linux is not.
