Because the UNIX based OS are based on PDP-11 architecture with the compromises required to fit in such systems.<p>Whereas already in the 60s, we had hardware systems like the Burroughs b5000 that could be fully programmed in Extended Algol and Espol, with zero Assembly.<p>The idea, as I see it, to base modern OSes in better older architectures that were lost to the mists of time.<p>Actually the mobile OSes, with their memory safe languages seem to already be moving into this direction.