That may be true, but there's all sorts of men's college teams, university teams, lesser pro leagues and even major boys tournaments down into the U16 age range that bring in thousands of people to watch the games, even though the level of play is significantly lower than the NHL. 

The Edmonton Oil Kings operate in the same arena complex as the Edmonton Oilers, and still get fans, despite the difference in quality of play, and both the uni and college teams in town regularly play to packed houses.

There's plenty of room for a women's pro league.