LGBTQ+

Or, why is it necessary only in women’s sports?

As a general rule in sports, men participate in essentially "open" leagues, while women's leagues exist to protect women from having to compete against everyone else to promote women taking part. In other words, women's leagues are already a form of protectionism to encourage participation because people care about women having a "fair" environment to participate in in a way they do not for men.

This idea that sports leagues for women/girls are a form of protectionism even extends down to school sports and Title IX, which is why under current Title IX policy girls must be allowed to try out for boys teams but not the reverse.