When we used to be told half the population was asexual

Nowadays one comes across articles in mainstream media about asexuality, such as this one at the BBC: What's it like to date someone who's asexual?

The asexuality flag.
I didn't know there was one
 until a few weeks ago. 

The general tone of this article and others like it is to express bemusement at the idea of asexuality. I.e. how could anyone not have sexual feelings?

I've got used to these kind of articles: they are quite common.

Then it struck me. When I was young (umm about 40 years ago), it was common knowledge that just under half the population was asexual. 

I mean women. Women were asexual. Women never wanted sex and never had sexual arousal.

Except for a small percentage who were nymphomaniacs. Women were either asexual or nymphomaniacs.

So now we are told that it is seriously weird that somebody could not have sexual feelings. When I was young it was seriously weird to think that a woman could have sexual feelings.

This is pure anecdata. I don't have evidence to back it up, but as somebody who grow up in the 1970s I think this is what pop culture was back then.  I'm not even saying that it was what adults believed then, but it is what pop culture pretended to believe.

There isn't an enormous point to this.

Except one.

Remember that our view of human sexuality is so strongly driven by what popular culture says it is, that a reasonable assumption is the following.

Just assume you know nothing about somebody else's sexuality unless you ask them and they are happy to tell you.