While completely true, I believe the average stats show women's rallies are longer, due to them not being able to hit nearly as many winners or completely dominate a service game like the guys do.

Update: I researched this and found an interesting research paper on the topic from the Australian Open 2017. Rally length and average point duration were similar between men and women. They should make the women go to the best of 5 format. https://www.researchgate.net/publication/326687553_Rally_pace_and_match_characteristics_of_male_and_female_tennis_matches_at_the_Australian_Open_2017