Same reason womens magazines are more popular than mens magazines and womens subreddits and websites are more popular than mens.

Maybe one day we’ll have full equality and it’ll be weird to think of “women’s spaces” as something that’s necessary. But it’s very much so today.

I don’t believe they actively intended to exclude anyone, but there is/was Dull Men’s Club, and I believe they’ve recently rebranded to “Dullsters”.