A phase out benefit makes a lot of sense if the reasoning behind parental leave is that the government wants to encourage a certain number of children. That is almost never the stated reasoning behind these kinds of laws. Usually, the justification is 'family-friendliness' or for the benefit of the child. In that case, there is no justification for a phase out. If the justification is 'family friendliness', then a phase out for certain kinds of families seems rather unfriendly. If the justification is the benefit to the parent-child relationship, which is shown to reduce certain societal ills , then it's not clear why only the eldest children ought to benefit while leaving the younger children to suffer a host of social issues, like susceptibility to crime, teen pregnancy rates, etc.
> Usually, the justification is 'family-friendliness' or for the benefit of the child. In that case, there is no justification for a phase out
Family-friendliness absolutely is a policy goal that encourages people to have children, but any such policy has a target population and also has limits. The objective of these policies is usually to assist median income and median sized families, not outliers.
An example of this today is the Child and Dependent Care Assistance Plan (DCAP) [1] which parents in the US use to pay for childcare with pre-tax dollars.
This benefit is restricted to around $5,000 a year, regardless of how many children you have. It also cannot be claimed unless all parents are either employed or are full-time students.
