because WTA fans'd rather be busy in tennis message boards fighting with each other, cursing at Mary Carrillo and Martina Navratilova or at ESPN and SkySport than actually being at tournaments cheering for their favourites...
Unfortunately, this is true.
Andrew's question does not have a single answer. It's a complex equation. There's a lot of factors.
In general, women's tennis is never going to have the credibility that men's tennis has. It's like golf--Annika Sorenstam was a tremendous player, but fans having to make decisions with their luxury dollars are going to want to see the best players they can, and that is men, like it or not. Bigger, stronger, faster and able to play week to week and create rivalries without their bodies breaking down. When people talk about the great women players of all time, invariably the names that come to mind are Chris Evert, Martina Navratilova, Billie Jean King, Margaret Court, Steffi Graf--players who could win 100 matches and a dozen tournaments a year and STILL play at the top of their games in the slams. That's credible women's tennis. No woman today can do that.
Livestream is a very nice luxury, but it has helped killed crowds for women's tennis. Take away the option to watch from your living room, and more people will go to tournaments.
Location of tournaments has a great deal to do with it as well. Put a tournament in a resort or wealthy retirement community, where people are not at work all day when most matches are played and you will see larger crowds.
Look, it obviously looks bad on TV to see the stands like that, but as a big fan of women's tennis I say go see them in person and show your support. I go to a few tournaments every year and always have a great time, empty stands or not. The players do appreciate it when there's someone there to cheer.