I'm not sure that this is a Shimbori decision or even a KT decision. There's no reason for them to not want to sell the costumes individually to NA, they make more money that way than in bundles. I feel like this may have something to do with Sony NA but I dunno. Either way they won't be getting a season pass 2 out of me so... Let's see what the tune being sung is when NA doesn't put out on DLC sales.
Free Step Dodge
NewWestFan
Derock
There's also Steam that doesn't individual packs as well. We're not sure what's going on but it could be Sony doing some sort of "censorship" in NA, according to rumors.
NewWestFan
We weren't expecting Steam to sell them individually lmao It's the downside you pay for playing on the definitive platform for the game I guess. I suspect there is some Sony NA influence though for sure.