Sex-segregation was done as inclusive measure - to include women into social life and sports. While race segregation was the opposite - to exclude black people from social life

Actually, sex-segregation was originally done as an exclusive measure - namely, to make & keep institutions and most of the public sphere for males only, and to keep girls & women confined mainly at home, in domestic work, in harems & brothels, or to their own section in synagogues, mosques and other houses of worship.

Sex-segregation was also instituted as a way of shaming, ostracizing or separating women from the rest of the world & normal life when undergoing specific processes of female biology - hence, menstrual huts, women being forbidden from cooking or preparing food when menstruating, and forcing women into long periods of "confinement" before & after giving birth.

In much of the world, sex segregation has been accomplished via laws and customs that kept women mostly at home, forbade them from attending school, restricted their access to transport, required them to be accompanied by male chaperones outside the home and to cover their heads and bodies whenever in public. Items of clothing like burquas and the head-to-toe chadors that girls & women in Iran were forced to wear after the 1979 Islamic revolution are basically portable cloth prisons meant to identify, stigmatize, segregate, isolate, physically discomfort and encumber girls & women as much as possible when outside the home.

As these examples illustrate, sex segregation be can be used as much to oppress as to help liberate women and insure our safety, dignity & privacy. Sex-segregation itself is not inherently a benefit or a drawback. Its impact varies depending on the specific reasoning behind it, circumstances surrounding it, & how it's implemented.

In the West, when schools, workplaces, major institutions & the public sphere gradually started opening up to girls & women, additional facilities for females like loos, waiting rooms and train cars were added to the already-existing ones long in use exclusively by males. But the reasoning when this happened wasn't always or necessarily to provide girls & women with safety, privacy, dignity and fairness - it was to keep girls & women out of the many male-only spaces that males wanted to remain male-only, such as the smoking & bar cars on trains, institutions of higher learning, certain professions, social clubs and entertainment venues.

Fact is, even after the world outside the home began to open up to girls & women, boys & men didn't want female people in their toilets, locker rooms, clubs, smoking lounges, sports venues, fraternities, grills, saloons, pool halls etc except as servers, cleaners, cooks and when working in some capacity to entertain and sexually service men.

Over time, women realized and articulated all the various ways that certain kinds of sex-segregated spaces in specific circumstances can and do benefit girls & women. As a result, over time women lobbied for & built a lot of female-only spaces - ranging from women's only schools & universities, women's loos & lounges, women's social clubs, women's hospital wards & entire hospitals, women's organizations, and in the 1960s & 70s, rape refuges and shelters for women escaping male domestic violence.

But when sex-segregation originated, & through much of its history even in the contemporary era, it was put into place & maintained because it's what men & boys wanted.