If you give a no-strings attached cash payment for childcare to a parent struggling with addiction or a gambling problem, they will probably not send the kid to childcare, and instead take the cash.

If you give a no-strings attached cash payment for childcare to a parent struggling with a paying their rent problem, they will also probably not send the kid to childcare, and instead take the cash. And then everybody's rents will go up because families with children have more capability to pay.

Nothing is ever a perfect system, but there are many more things wrong with the current system than concerns about the equity BETWEEN different working class families in different situations. Some of those dysfunctions will happily consume most of an incrementalist policy solution to an arbitrary problem. Direct provision or vouchered provision of necessary goods and services has a lot of minor problems, but it happily mitigates our ability to let one problem eat an unrelated solution.