Yes. Remember the Olympics. The discussion why women's shorts must be tight and men's short must be loose cuts. There is no reason why an athlete must wear one sort. Due to making competitions fair it can be useful to agree upon a sort of sportswear that doesn't affect fairness, but why it that agreement in case of women means tight tops, tight shorts and nude bellies is beyond reason. The sportswear of that type does in fact show off the body in a way that is unrelated to the activity. If you can see the curves of breasts, labia, nipples or such or not is not relevant for sports. So why do we not have the situation that we also see testicles and penises moulded by tight shorts? I am a body positive person, I do neither object tight shorts, wide shorts, nor do I object to see penises, breasts, vaginas or such. I also would not object to have the Olympics like in the old times, athletes in the nude. The commercial operators would oppose that due to the fact that all the bigots would not attend. So it might not be a sexist thing all together, it could be that the old silly men in the Olympic organisation are more sexist than ever, but in the commercial environment sports do live in sexism IS a factor.

It doesn't necessarily have to mean that women's sports aren't worth watching. Sexy uniforms would make them more appealing whether they were worth watching already or not. And if people found women's sports not worth watching, would that necessarily be sexist? What if men are generally better at sports than women? Or what if people prefer to see big, burly bodies playing sports? Wouldn't that be completely fair? Or what if more men like sports than women, and they'd just rather watch other men play them because they relate to them more / they're in-group? And I don't think the other side of it, preferring to see women in sexy clothing, is sexist either. It's just the way men are built. We love women, and sexually we're very visually oriented.

Also the people who choose to put them in sexy clothes are probably corporations, and the decision would probably have been made for the sole purpose of making more money, though of course that alone doesn't make it impossible that sexism would be involved--it would just be solely on the part of the viewer whose biases trickle up to corporate decisions.