Oftentimes what these events actually are for is more about solidarity than recruitment. One of the issues with male dominated fields is that oftentimes they are exhausting to participate in when you are treated as an outsider. Having a community space where people can get together and talk shop, ask frank questions about culture from recruiters and gather strength from visibly seeing other people doing the same thing you do can give a sense of not being so alone.

That and a lot of women require a lot more data on how they compare before they feel like they are actually a viable candidate. They are sort of trained into an almost crippling idea of modesty and more social anxiety in general so a lot of them will only apply if they solidly fit the listed requirements. When they utilize a dialogue based recruitment space they can gain confidence that small missing bits of listed experience desired on their resume don't fully discount them from being a candidate for a job and gets more of them to apply. Women lean on pack tactics more than men do so these sort of events actually fufill a lot of secondary objectives than just on the day hiring.