In an article from September of 2005, Matt Cavotta tells us about the Magic: the Gathering Style Guide. I particularly appreciated this quoted bit:
Feel free to paint beautiful women, as long as they're shown kicking ass. No damsels in distress. No ridiculously exaggerated breasts. No nudity.
Combine that with:
Remember, your audience is BOYS 14 and up.
And you get a directive that the demographic of boys 14 and up be shown women kicking ass and not being rescued all the time.
Of course, you still have the angels who like to go into combat with bare midriffs:
Art from Serra Avenger
...but you also end up with coolness like this:
Art from Braids, Conjurer Adept
Isn't that cool?
I think it's cool.