The thing is that it's so easy to change the pictures in to black and white later on, it's almost limiting to just have it in black and white. A picture might've been really nice in color, but then you just have it in b&w and you can't turn the colors back.

This is why I always tell everyone to never take b&w pictures. Though I do agree that sometimes you just might want to upload a picture really fast from your device in b&w, so would be nice if there was a function for this. And no doubt they'll add it later, hopefully with the face recognition bits and other additional stuff