Some shutters are inside the glass, some outside. They are all used, not ornamental.
The reason they are there is because, in stone, stucco, or brick construction, you have natural daytime air conditioning if you don't let too much sunlight in during mid-day. You will never see air-conditioners, because they don't need them except in modern office buildings.
The low-humidity Med climate, with cool nights, is perfect for humans with stone buildings.
I just stumbled on the random fact that Hartford CT, Cape Cod, Rome, and Istanbul all exist on latitude 41 N. Of course, just along that latitude is not the quickest route. Great circles and all that.