It's utterly ridiculous and frustrating, and I say that as someone with a fairly switched on DH!
Case in point, it was his mother's birthday last month, it was a milestone birthday, I'd said to him after Christmas to think about getting things organised for his mum, to get him and his brother to figure out a plan between them on what to do.
Time marches on, I mention it again mid January, he replies yes, yes, I'm getting presents sorted etc, I'll do it. Ok then. I say again, it's a milestone birthday so you'll need to sort something like a meal out, arrange that, he says yes, yes, I'll sort out.
Gets to the Feb break, we are away for a few days with his mum and my dad, I mention to her casually when it's just her and I if she is looking forward to her birthday and what she'd like to do? She absolutely hammers into me, what do you mean, I thought you were arranging it?!!! I say, uhm, no it's up to your son's (DH and his brother). She then goes quiet and I think, oh FFS.
So I reiterate AGAIN to DH when we are alone, you really need to get your shit together, your mum's expecting a big thing, you've not even bought presents yet FFS, you need to book a restaurant, invite wider family, friends she wants etc, you need to do it now. DH panics and goes, oh she wants something?! YES!!!!!
He then messages his brother who predictably has also given it zero thought (his brother being single and living with his mum btw, so it's not like he doesn't have spare time or inclination).
With my help, they get a restaurant booked, they invite all the main friends/extended family and everything is sorted and MIL is happy, gets a nice meal out, lovely presents and is delighted. DH is apologetic to me and I think, well if I hadn't said anything, what would you have done? It's basic. It's so fucking basic. And he is, generally, a good man and agrees and is understanding of all the bullshit to do with patriarchy and social expectations of women. Yet he still dropped the ball. I honestly despair.