Men didn't start that. Granted, some of them like it and do expect it now, but they were not the source of that cultural change for women. Ever since the 1970s women have been told that in order to be liberated and equal to men they should behave more like them. They were told that by other women. By feminists. (And, granted, by the Market who wanted their cheaper labor and their money:
https://archive.ph/LvSIS . ) No cultural niche was omitted either, from family and working norms to sociosexual ones. Cosmopolitan magazine was the pop bible for that. It was endorsing indiscriminate promiscuity (and the promise of liberation from practicing it) for women in every way imaginable two decades before the internet fired up. All kinds of social stigmas were deconstructed in its pages. Screwing married men, becoming an "escort" etc. Erika Jong in 1973 wrote about the idea of the "zipless fuck" for women in her book Fear of Flying. Which was anonymous sex without difficulty, strings, risk, etc. A "Wham bam thank you Mr.!" for women.) If you didn't desire a zipless fuck now and then for yourself as a fun vacation and affirmation of your sexy worth, well, you were a social dinosaur, uptight, prudish, etc.