wellinformedyid,
there is a well known halacha called mechitzos in a shul. The reason being is because of the sensitivities of the people davening, because Halacha knows that men will get distracted if they are around women. I wouldn’t be suprised that the reason there is no halacha about women congregating the streets is because they didn’t if they did then there would be one, taking into account mens sensitivities.