IDK, in my household, I am the one who watches the Mercury games. Most women from my generation aren't into sports that much as a whole. Of course someone will point out exceptions in their family. My Daughter in law is the biggest Niner fan ever. But all the women in my family? Nope. I think it's more cultural in the USA that women cede sports as a man thing. A lot of foreign women I have met are more likely to go to women's sports in their countries. I just think it's a cultural thing here. About the only team I see being even supported similar, and it isn't even even yet, is the Women's National Soccer Team. That's probably the familiarity with soccer moms to the sport.
It shouldn't be all about women only supporting the sport. Men I know won't even give it a shot. I took my boys to a Mercury game and they said they would go again., Would they have gone on their own? They both say no.
Finally, we have a LOT of sports in the USA. Professional, College, etc. There will be winners and losers just because we have SO much to watch. Maybe the WNBA should be in underserved markets. Here in Phoenix, there's so many sports to watch, they have to compete against the sheer volume alone.