That's a good question. I've just come back from the Christmas markets in Frankfurt, where I used the GR exclusively. I had the hood on pretty well all the time, partly to improve my grip and partly to shield the lens from occasional drizzle and the odd bump. I find myself generally fitting it about 50% of the time, often just the tube, because I like the handling with it attached.
Duh! I just thought of something. Why should I pay $696 for the GR at Adorama when I can spend $896 for a special edition of the GR in vintage metallic green body with wood grip? My very own Hasselblad Lunar!