In which I am frustrated by news reports

Why is it that criminals' gender is never specified in news reports unless the criminal is female? "Mr. so-and-so was murdered by a female assailant. She was arrested the next day." The murderer's gender has nothing to do with the story. Even if you want to include it for the man-bites-dog factor, you already have "she" in there, so why do you need to specify "female"? Same with "Bob Smith is a male nurse."