"They don't want to do it"
Ava doesn't want to do her shoes. Leo doesn't want to pack his bag. Maya, offered the form, looks at you as though you've handed her a tax return. That's true, and I'd ask you to consider why it's true, because I don't think the wanting was ever absent. I think it was there and it was handled.
Chapter 4 had the finding that the wanting to do it oneself arrives early, uninvited. The interesting research is on what happens to it afterwards, and the best I've found comes from Mexico. Lucía Alcalá, Barbara Rogoff and colleagues asked mothers in two communities in Guadalajara about their six-to-eight-year-olds. In an Indigenous-heritage community, many children were reported to take on complex family work on their own initiative, minding younger children, cooking, running errands, without being asked. In a community with generations of Western-style schooling, few children were reported to contribute to household work at all, and seldom of their own accord, and those children were more often in activities that adults organised. In a companion study, Andrew Coppens and colleagues asked sixteen nine and ten-year-olds directly, and almost all of them said that children want to contribute to the family's work. The samples are small and it's reports rather than observation. But it's a picture of the same wanting going two ways depending on what the adults around it did with it.
What the adults do with it, in the households I'm writing about, is the takeover. The two-year-old who wants the spoon gets fed because it's quicker. The three-year-old who wants to help with the washing is given something else to do because the washing takes twice as long with help. The five-year-old who wants to crack the egg gets to watch. Each one is reasonable. Together they're a curriculum, and what it teaches is that this is the adults' work and your job is to wait. By nine the lesson has taken, and the child who doesn't want to pack the bag is a child who learned, correctly, that the bag was never theirs.
I'd notice, too, what "want" is being measured against. A nine-year-old doesn't want to pack a bag in the way they want a biscuit. Nobody does. The question isn't whether they'd choose it but whether they'll do it without a fight once it's plainly theirs, and the answer, in most houses, after the first fortnight, is yes. The fight is about the change, not the job.
So "they don't want to" is true and it isn't the end of the argument. It's the result of the argument you've been winning for years. It can be unwon. It just takes the same fortnight.