Swear words: check. Sex scenes: check. Inter-racial relationships, gay relationships, unedited childbirth: check, check, check. But film and TV have one last taboo that it seems totally incapable of facing: not having sex. Bad sex maybe, good sex definitely but exploring what happens when people don't have sex for a while is not considered appropriate viewing.

Apparently at least one in five of us haven't had any in the past month. For women it's higher. For those aged 16 to 24 it's higher. Basically, a lot of people aren't having sex (and remember, that's only the number of people willing to admit they're not having sex).

It doesn't seem like 20-50% of the adult characters we're shown on screen share the population's experience – those that aren't seen actually having sex or talking about sex never talk about it. So you're left with only stereotypes to assume whether you're supposed to believe they're doing it. That's not dissimilar to other types of sexual behaviour previously deemed "deviant" like homosexuality.

When sexless characters do make it on to the screen, they almost always fall into two distinct camps. There are the "losers" – unsexy geeks like the 40-year-old virgin or freaks who don't want to have sex because they're either too odd or religious. Then there are the "past its" – the old, the married, those who apparently just don't do it any more.

That doesn't resemble the statistics. Sexual existences aren't perfectly binary between having it and not having it. (Though maybe the perception that there are such distinct eras in our sex lives is a reflection of just how obsessed society still is with the notion of virginity). In reality, most people continually go through phases of frequent and less than frequent sex. Why don't scriptwriters tell us that someone somewhere not far away is another one in five? It would mean 20% of viewers feeling less alienated or ashamed about their sex lives.

So I tried to talk to people in my life who are in the silent minority. The reaction I get is mixed. A bisexual friend tells me that she wishes she had had less sex when she was younger, explaining that she learned more about her sexual preferences when she wasn't having sex than when she was. I ask another friend who hasn't had sex for four months. Her eyes go wide, she grips the table and leans forward – I get the idea. It's the uncertainty that's distressing her – she can cope with not having sex now but she can't cope with not knowing if she won't have sex for another year.

Sometimes, characters who aren't having sex are seen as pitiable but most of the time, whether they can't or won't do it, we're just supposed to laugh at them. That might just be escapism because for some adults, not having sex is not much fun. But then neither is being physically attacked or getting cancer and yet those are plots that producers don't shy away from.

Those producers are missing out on the chance to engage with people by depicting on screen an important part of their off-screen lives. Here's a suggestion: a sexless character that isn't a hopeless, horny, prepubescent boy or senile great, great grandmother but someone who just happens to have not had sex in a while.