What is the purpose of the spine card? If I get the game with case, disc and instructions, I consider it complete spine card or not.
The purpose of a spine card is to provide a standardized label for shelving purposes that can be read by your average Japanese book/music/game store employee. It also has the bar code. This way they can release stuff with cover art unmitigated with logos, translated text, etc that are of no interest to the eventual buyer. For example, keep in mind that the vast majority of Japanese music is f*cking terrible, so they are going to end up listening to a lot of stuff from Europe, America, etc. Rather than paying an army of graphic artists to make katakana logos for Yes albums all day they just put an obi in there.
So, in other words, the obi is slightly more meaningful than the receipt that came with the game; worthless. I throw away all of mine immediately*. It keeps me from going over the edge of otaku reason.
Of course compared to stuff like US Sega CD/Saturn cases, TG-16 Boxes, and other things that are literally designed to take up space and have no other purpose whatsoever, the obi is extremely practical,
and you can just throw it away, whereas with a US Sega CD/Saturn cases are still taking up twice the space on my shelf as they should.
I find it strange that game people keep dumb shit like US TG-16 boxes. I mean, for over a decade audio CDs released in the US mostly came in "long boxes" which were huge ugly cardbord extensions designed to make small 5" CD cases compatible with bins originally build for 12" records. Some of these actually had interesting stuff on them (usually it was just a blown up version of the normal cover art) but I'm pretty sure I've never once run across someone who kept these things, or a shop selling them, or an eBay seller, or anything. They just got chucked instantly since people pretty much just though of them as a huge waste of cardboard and not much else.
Anyway, I'm surprised that nobody has yet mentioned that Working Designs games, Super CD or not, often came with a cardboard slip case. Not a box, but more than just a normal jewel case.
*Except for the one that came with CvS2 (DC) because it says, "2D Will Never Die" or something like that, which I took is a very ironic statement at the time, and it was since they pretty much don't make anything 2D anymore.