The New York Times reports that Nike is starting a new ad campaign featuring 18 athletes who happen to be women, whose basic message is: "We’re athletes, so ditch the female modifier." Much like the welcome trend of dropping the word "Lady" from team names, athletes are making clear that they are just that -- athletes, and that there's no need to distinguish them as "women athletes".
Use of the term "women athletes" serves to reinforce the norm that "athletes" must mean men, and therefore if women are playing sports, that must be clarified by using the modifier (our culture uses many terms like these, in which the modifier implies that the term naturally belongs to another group -- for a derogatory example with racial implications, consider the term "white trash"; for a derogatory example related to sex stereotypes, consider the term "male 'ho").
At any rate, the ad campaign serves to reinforce the message of Alvina Carroll, a streetballer, on being an athlete: “It’s not a girl thing. It’s not a boy thing. It’s a skills thing.”