The idea is for the child to understand that their parents love them, raise them, and educate them, but that as a member of the family, they also have responsibilities and obligations, and that later in life, they will have to pay for many of the things that their parents give them for free. It is important to make sure that the child understands and realizes this reality, rather than living with their parents at their expense until the age of 40+, as sometimes happens...
Yeah, that’s just one amongst several ways of parents prepping their kids for what’s ahead. But the truth is that there should be some sort of age limit for this kind of preparation, some parents feel like as long as their kids have started earning some money, they should automatically start paying rent or share in the bills, regardless of their age, which in my opinion isn’t the right way to go about this.
This is probably also an extreme. It is wrong to demand that a 5-year-old child pay for housing, just as it is wrong to support a child until the age of 45!

There is no ideal advice, specifying the exact age of the child, family income, or child's income, when to start such a conversation.
But you shouldn't shield your child from understanding how adult life and commodity-money relations work. As I have already said, a child should not think that everything they want should be fulfilled immediately. They should understand that in order for them to have something, their parents have to work, and it is for their work that they receive money, which they then use to pay for housing, utilities, food, children's things, and toys.
And here you need to smoothly lead up to the idea that being independent, including financially independent, is good and convenient.