But a movie with a single female character is perfectly capable of propagating strong female roles, right?

And strong female roles are important, but they're not the object of discussion here. The Bechdel test is about normal female roles. It's about measuring the narrative warp present in Hollywood. "Two women talking about anything other than a man" isn't about being strong, particularly as it's passed with "two women talking about a sandwich" or "two women talking about the weather."

I find it a valid complaint - two guys can shoot the shit in any movie anywhere. Two girls don't shoot the shit unless it's a chick flick. As I've discussed before, there are any number of non-deliberate ways that it happens, but unintended bias is still bias.

As a writer, I pay attention for the simple fact that abiding by the Bechdel test gives you a bare minimum character depth for no loss to you. You don't need to change your story, you just need a role that belongs to a female for reasons other than romantic entanglement. Considering women are half the population, I think normalization is a worthy goal.

I know how it started but why on earth did it catch on in mainstream media? People take it semi-seriously.

Blame Sweden.

I mean, putting aside whether the inclusion of a made-up character in The Hobbit was criminal, she's basically there because one of the long-standing criticisms of Tolkien (and fantasy in general) is his relative lack of female characters -- so now because of the attention paid to "strong female roles" in Hollywood, little girls can go see that movie and have a role model.

It's important to note: the Bechdel test does not require quality. And you'll get no discussion from me on The Hobbit - I hated the book and the first movie was dreck.

My point is she never has a real conversation with a female character but who cares?

Conversations need not be real - that's the whole point. "Fuck, I sure love rainbows" counts. The argument is not that women in cinema need to be momentous, it's that they need to be - they deserve to be - normal.