I believe porting these OS to classic Amigas is just some days of patching and hacking. The problem comes after releasing it for these platforms, with all the hardware fixes/patches and hacks it is hard to assume that the software will work properly on every single configuration, and the resources to do the fixes are big. That's why the developers of these OSes, prefer to release them only for new hardware and not for the 11 years old PPC boards, attached to some other even more vintage boards. Supporting classic Amigas with new OS looks more trouble than profit.
