At work, my boss walked in with a new sports jacket. He complained that there were no pockets. It was pointed out to him that expensive jackets sometimes are sold with the pockets sewn shut,& you are expected to open them.
Why is this? 
My understanding is that this keeps the pocket from getting all “slouchy” as the coat is shipped around. It keeps it looking tailored and well-presented. The kind of pocket that’s usually sewn shut is a besom pocket, which in a men’s coat is at the front bottom.
This gentleman should be using the inside pockets to carry stuff anyway, so he really wouldn’t need to cut the pockets open. I (a lady) have had suit coat pockets that I never opened–to keep myself from stuffing stuff in there and looking like a slob.
gigi’s right, except that often the breast pocket is also sewn shut, and sometimes the inside pockets are as well. The pockets are closed with what my mother used to call (I have no idea if it’s the correct term) “whip-stitching” and can be clipped open instantly with a razor blade, or better, if you have one, a seam ripper.
Yep, whip-stitching is a open, long stitch that is seen from the outside so can be easily cut. It’s also used for hand-applique and basting, because it “whips” along in bigger stitches that are often temporary.
::wanders off to find something to quilt::
I’ve been told that its done to keep you from putting stuff in your pockets, thereby ruining the line of your fine natty coat. If you must insist on putting something in there, you can cut the stitching.
I don’t think it’s for the shipping, I think it’s because the first thing people do when they try on a jacket in jam their hands into all the pockets. (Maybe they’re looking for change?)
After it’s been tried on a couple of times it just doesn’t look so good, the pockets kind of slouch.
Sooo, they sew them shut, that way no matter how many people try it on it still looks good.
That’s my WAG.