Care work is undervalued because, for most of history, women supplied it for little or nothing. A price that was held low for that reason gets read as a sign of low worth. The same undervaluation helps explain why women earn less than men.
Most societies kept a large supply of care by strictly limiting women's freedom. Once those limits loosen, the care does not appear on its own. Someone has to agree on new rules for sharing the responsibility, or the people who need care pay the price.
Harder market competition rewards people for chasing their own interest and punishes time spent caring for others. Care for children, the elderly and the sick is essential, yet markets do not provide enough of it. Left alone, competition can drive caring and families out of business.
Caring relationships are partly a trade and partly driven by real concern for the other person. People care for reasons other than money. That is why care resists being measured with prices, and why paying for it never fully captures what it is worth.
Standard economics tallies what gets produced but ignores the unpaid work of raising and sustaining the people who do the producing. Without that work, neither families nor markets could continue. Moving more time and money toward children also has costs, which then fall on other groups.