I know even in my generation it seems to be bloke normally drives, woman normally passenger, but as I don't know people who drive much I haven't seen the swap thing.
In our household MrNC usually drives, partly because he'd been driving for 10 years before I met him and then I only got my licence after we'd been together a few years, so he can drive automatically but I have to think about it and be very awake (like what I'm not now I have a young baby...) Also he is terrible at navigating, whereas I'm excellent at it, even when I'm asleep and get poked and asked which way at some junction! Unlike the satnav.
He's a bit of an anxious passenger as apart from me he's only been a passenger for his dad who is an ex-rally driver, drives like a maniac, and is the only driver to ever make me carsick! However he does keep his mouth shut after I told him once to shut up or get out, but the clutching the doorhandle is annoying...
I try to drive more now as ds referring to 'Daddy's car' gets on my wick, and ds aged 3 doesn't understand the vital role of navigation...
With my parents, my mum used to drive more as my dad hated driving, but then my dad got used to driving overseas and got given a lovely company car to keep after retirement, and then my mum crashed it three times into inanimate objects and thankfully gave up driving (she was just as bad beforehand!), so dad does it all now. So ds refers to 'Grandpa's car', but at least that's accurate.
Given how most women are in relationships with somewhat older men, most men will have more driving experience than their partner, leading to this skew I think. And that's before the difference in how many men get driving lessons for their 17th birthday compared to women and how many men/women get a licence at the same age.