I have heard a couple personal accounts of people who were genuinely uninterested in [insert sex here] for decades, and then something changed. We still don't really know what causes sexual orientation or how it develops. So I'm willing to believe that—for a small handful of people—their sexuality really has fundamentally shifted over the course of their lifetime.

And then bisexuals do make up a sizable portion of the population. And there there are Kinsey 1's and 5's, who might not really experience themselves as bisexual in general, but still sorta are. If people were down to use words like heteroflexible and homoflexible that might help? But in practice people don't really call themselves that.

But yeah. No matter how we got here, it's a real bad situation.