The reason is that it runs too big! I got in XS and it was huge on me, I am 5'1 and 110 pounds. I always wear sizes XS and sometimes Small. I got in Birch Heather and I thought it would be something like Oat colour but it wasn't, it's a very very light beige and I think it looks a bit boring! I love classic colours like beige and oat but this one was just too light, so I guess it looks like a dirty white colour, which is not nice. But I liked the quality of the piece and the style overall.