When it was announced that NieR was receiving a spin-off, fans of the series were shocked. When Platinum Games was revealed to be the developer, fans celebrated. When the news broke it would be coming to PS4 and PC ‘only’, not all gamers were happy. 

NieR Automata Producer explained the reason why there isn’t a Xbox version. 

The main reason for this is that the Japanese market for Xbox One is not strong, so the decision was made to focus on PlayStation 4 rather than to split our efforts across two platforms.

That answer makes sense. Japan has never accepted the Xbox like the rest of the world has. He continued.

The biggest benefit to developing on one platform is that we did not have to split our time, allowing us to focus more on the quality.

It is not about whether one platform is better than the other, it’s that from a development point of view were can devote more time to one platform.

Pure business decision. No console war or fanboy jargon. Nice.

NieR: Automata hits the PS4 and PS4 Pro on March 7 US/ March 10 UK. 

(Source)