Yes, because machine code for the legacy machine is how the game was made, you can’t be 100% sure that recompiling it for other platforms won’t introduce bugs because of the difference in platforms. For example, the original Space Invaders used the CPU to it’s maximum to render all of the invaders, they weren’t normalizing by the dt between one frame and the next like we do today for most games, so this results in the game running as fast as possible, which in turns translates to the less enemies on screen, the faster they move. If you recompile that binary for a modern system it’s game over in less than 1 second, because current hardware can handle all of those spaceships as if it were nothing.