I dunno, I don't really think it's that weird.
I mean, first of all, obviously there's a reason why fighting game girls wore skimpy clothes, and that reason is because game girls are hot and players want to see them running around in sexy outfits. But more importantly, "protection" is a complete non-issue! Think about the games these women are in, and the combat situations they find themselves facing. These aren't like medieval battles or modern-day war zones where body armor is the norm; they're street fights and alleyway brawls, where heavy armor would be rather impractical - hell, in a few games, like Mortal Kombat, body armor might actually hurt more than it helps (if you can be burned to death or frozen alive, a little extra speed is far better than a big heavy breastplate) For example, look at T-Hawk and Casey Jones. They aren't wearing anything that offers them "protection"; they're wearing jeans and vests and t-shirts! They can get away with this because armor is unneccessary (unless you're a Big bad, like Shredder or Shao Khan, but they tend to wear armor only because it looks cool) I mean, I know there's a "chainmail bikini" meme that critiques sword-wielding fantasy/barbarian women (while never commenting on the fact that sword-wielding fantasy/barbarian men tend to wear even LESS than their female counterparts- a studded-leather jock strap, if they're lucky) but I don't really think it applies here.
In fact, I think I'd go one step farther and say that wearing super-sexy clothes is an advantage for these women. There are two reasons for this: first, super-sexy clothing is very, very, VERY distracting. All it takes is one second of hesitation while Mai Shiranui flashes her panties at you, and BOOM, she's through your guard and you're down for the count. Also, I think it's a scientifically-established fact that sexy women are less likely to be killed by victorious male warriors. Generally speaking, men are considered disposable, but women are not, and the cuter/hotter/fitter the women, the more valuable her continued existence is seen to be. If you defeated a smelly hideous chud like Baraka, you probably wouldn't think twice about smashing his skull in; but if thong-girl Mai Shiranui was lying at your feet, I think you'd probably show her mercy, wouldn't you? In other words, skimpy clothing gives our heroines a small, but possibly critical, psychological edge - both during, and after, the fight.
