When the iPhone 3G came out I got it in white because I thought it looked really slick. Every iPhone I've owned since (4, 5, 6, 6S) has been in black because I don't like how the front is white on the other option.
Now that the X has the same front whether you get white or black, perhaps demand will be the same. I'll probably end up getting white to try something different. I'll most likely put a case on it anyway.