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Does anybody know the reason?
Perhaps it is because the game got a mixed reception at release? They did add rollback netcode and the reception was quite positive to this, rightfully so. However, many people claimed the port was bad for not having a training mode, which is odd because not even the AES nor Neo-CD versions of KOF '97 had training modes. People also experienced glitches at launch apparently. I never experienced that issue as I got the game after rollback update, even though I almost never play it online.

I guess my point is that due to a rocky start, the game did not sell as much as they would have hoped, thus they do not see a reason to put it on here. If that is the case, then that is a shame because I would have got it again for goodies. As well as the fact that I want to support SNK and this platform to show SNK that DRM-free gaming is viable for business. Plus there is a great opportunity to add cross-platform online play. Idk, I guess we can dream, right? Other than my own speculation, I can't really say what the reason is for sure. In fact, I am going to ask in the Steam discussion forums, as I also want to know why its not on here.