Cause the Xbox One has the best chance of winning those territories simply because those countries make up a bigger portion of it's sales, while the PS4 has a more even distribution worldwide. The 360 also took last gen for the US and UK, and from what I've noticed at least is that a lot of 360 owners buy right into the kind of games that the Xbox One caters (Halo, Gears of War, etc.), so if they had a choice between the two evenly matched consoles they'd go with the ones with the games they like.
You're Gonna Carry That Weight.
Xbox One - PS4 - Wii U - PC