Not really, considering the spandex smooshes the boobs together and against the chest. And most sweat gathers on the underboob (damn you, underboob! Refusing to ever be dry!) All of the cleavage sweat would be in the cleavage, not on top, so none of that sweat would have a chance to dry.

It serves zero function other than "Quick, be distracted by my boobs! See? BOOBS! I AM A FEMALE SUPERHERO, LOOK AT MY BOOBS"