I find these wooden boxes to be somewhat of an annoyance. It seems that they need to be protected as much as the pottery inside. When I recieve them, I remove the item from the wood box, re-tie the ribbon (improperly, of course), re-wrap the wooden box in the bubble pac, throw it back in the shipping box and put that in the closet. I'm actually happy when I buy something that comes in cardboard. Some of the wood boxes are very nice, but they can take up a lot of space.
These boxes vary tremendously in quality. Some of them are near works of art in and of themselves, as Picasso noticed. Others are cheap junk that are supplied by the importer to boost the esteem, and the price, of normal objects that come from the kiln without a box. Many boxes aren't signed, as the items inside may come from a kiln such as Somayaki where individual artisans don't normally sign boxes and in many cases it would be meaningless if they did. These items are hand-made and of high quality, but many hands are involved in the manufacturing process.
Even legitimate, artist signed boxes don't always come with a ribbon. I've purchased five Aohagi items made by Noutomi Susumu. All came in signed wooden boxes, and none had ribbons (no complaints here!). There are actually paper bands that slide over the box-lid combination and hold the lid in place. This artists items are not cheap, and they may deserve a better box or at least one with a real ribbon, but I don't care because the items inside the boxes have been of extremely high quality.
I've heard that one very well known artisan never signs his boxes. I read a warning from a legitimate seller that many sellers on Ebay claim to be selling his works in an artist signed box, and that in these cases, at a minimum, the box is not legitimate even if the item inside is. Either that, or the seller can't read Japanese and assumes the signature is there.
I received a Bizen sake set yesterday and was quite surprised by the quality of the box. At first I thought a piece had separated during shipping, then I realized it had a slide-out lid that wasn't pushed in all the way. There are grooves near the top of the box and the wooden lid is placed in the grooves and slides out when you wish to remove the sake set. It is very well made so I'll need to find another space in the closet.
Although many high quality items come in boxes, so do many items of lesser quality. I wouldn't make a purchase decision based on whether or not the item comes in a wooden box. I have seen some very high quality items that come in cardboard. Sometimes this is due to the items shape or size, which may not fit in anything but a custom made box. The boxes, of course, boost the price of the item, sometimes significantly.