Bechdel drawn her seminal cartoon in 1985. Consider how different the world was then. That we’re even discussing something as basic as two women talking in general conservation should be the only point.
There are dozens of shows today with women as producers, writers, and stars, and even many with all-women casts. Huge advances, sure. But looking at the highest grossing movies, i.e. most popular, most seen, and most like what Hollywood wants to make, reveals that women are usually at most mixed into a large ensemble cast, still interacting mostly with the male leads rather than one another.
Look at this post I made in the “How ‘woke’ are movies really” thead.
I’m sure that many of those movies pass the Bechdel test, but that’s not obvious from their descriptions. It takes an absolute female-starring film like Wonder Woman to be obvious. That’s why it’s still a thing.