Given that the CPU went from PowerPC on the 360 to x86 on the One it's not surprising there is no backwards compatability. And before somebody says "Emulators!", stop. Just stop. Emulation is only successful if you can get 1:1 performance based on the old hardware, and that's damned difficult to do. Otherwise you're just wasting people's time and adding on frustration. Don't believe me? Remember that the Playstation 3 launched with Playstation 2 hardware on the same board to allow for PS2 games to be played. That lasted one generation. The second generation went emulation, which worked for a lot of games but not all (I had about a 75% success rate). Third generation of the PS3 hardware? It was gone, and aside from the gnashing of teeth by a small group of gamers nobody really missed it (much like Linux on the PS3).