As I understand it, the primary reason that there are women-only events is because some people worry that having only open events would discourage women from participating at all. The reasons why women might not want to participate in open events seems to be related to women and girls historically not being encouraged as much as men, and therefore being weaker performers (as a group) than men. Additionally, there have been issues with sexual harassment (see the recent lichess article "Breaking the Silence"). It's understandable that some women would not be comfortable competing in that type of environment.

The main goal is to attract more women to chess as a sport. Women historically have had fewer chances to participate in pretty much anything compared to men, so it's no surprise that women are underrepresented in chess and that chess is viewed as a men's sport.

If this is supposed to change at any point, it needs to be visible that chess is a viable and inviting sport for women. It needs to have female idols and role models competing on the highest level. If Ju Wenjun was not Women world champion and there was no women's section in top events, I doubt the majority of the chess community would know who she was. She would just disappeared into the sea of 2500-2600 GMs struggling to make a living in chess. In terms of viability, there is of course the topic of chess as a career. It is hard to make a living in chess, only top player will have a somewhat stable income playing chess. Most players make money doing something adjacent, eg. coaching, writing or streaming. Having a dedicated women's category also means dedicated price money.