Because the clothing of any character in the series has never been qualified in the story. There is no definitive Lin Kuei, Shirai Ryu, Special Forces, Shao Kahn's Soldiers or extermination squads, Black Dragon, Red Dragon, Edenian, White Lotus, Shokan, Chaos cleric, Wu Shi, God, or even Elder God costume/uniform. They have all changed in every game, and even when multiple characters from the same organization have been together, the outfits vary. Not even the logos stick. The only people who wear relatively similar clothes are the tarkatans, which is ironic, since they are the wildest of the bunch. Them and the Shadow Priests. And maybe Hotaru's guard, but they were only really seen once. Meanwhile Smoke, Sub, Tundra, Sektor, and Cyrax all appear in MK9 with completely unique outfits. Even their robot forms have different designs and colors, which are never said to be related to rank or term of service or anything. All that's been said about clothes in MK is that the Shirai Ryu wear a yellow "version" of the Lin Kuei outfit to spite their former allegiance and that Sub II wore Sub I's outfit in honor of him in MK4, oh and the armor in MKDe is a cryomancer relic.
So again, while it may be shit writing that now it took Undead Scorpion two tries to kill Sub instead of one, it still doesn't actually change anything in the story.
Mythologies does suck, but NRS has done the best job of advancing and keeping track of their own story more than anyone else in the fighting game genre. A lot of characters matter, and generally speaking the defeat or death of certain characters at least gets referenced in the follow up games. Meanwhile, SF retcons itself with every release. KoF has MASSIVE gaps and never explains what happens to half the cast. Soul Calibur told the exact same story 3 times in a row, then fast forwarded 20 years just to tell it over again with new characters. Guilty Gear, same deal. Tekken reduced half its characters to jokes and can't decide whats canon and isn't. Most other fighters don't even bother trying to tell a story, the only one that came close was Bloody Roar and that game is dead.
BlazBlue is the only other fighter that comes close in terms of actual canon involvement to the game and its a convoluted mess of time loops, inexplicable artifacts created by people or events that are never explained, other random acts of magic, and characters that get possessed or cloned or otherwise repurposed for whatever their personality needs, and good old fashion deus ex plot twists. It has a ground breaking 8 characters that represent three actual people in the plot, and several others don't even have a role or explanation in the plot, they're just there to pad out the roster.
I'll take Scorpion showing up in a prison cell in the wrong pajamas over Platinum the goddamn Trinity being a character from the past, present and future simultaneously any day.
