because that statistic that people throw around all the time (the 70-ish cents on the dollar one) doesn't mean what a lot of people think it means. The study that number is pulled from did not show that women get paid 70 cents for every dollar a similarly qualified man in a similar position makes. In fact, that study showed that similarly qualified individuals in similar positions made the same amount regardless of gender. The disparity that study did show, was that there were more men in high-income positions(CEOs, university deans, etc.) and more women in low-income positions(waitress, secretary, etc.)

If employers could get away with paying women 70% for the same work, they would. But they can't, so they don't. That isn't what the wage gap is. The "wage gap" just shows that if you take every woman in the country and average their salary, it comes out to less than the average when adding up all men in the country. Some of this is sexism, some is cultural/societal differences, some is just preference (there was a sex discrimination case against sears way back in the day for not having enough women in the higher-earning commission sales positions. Turns out women just didn't apply for them, rather than intentionally being denied.)