The ONLY legitimate rationale is to allow a caregiver to forgo additional income in order to provide additional care and supervision of children. Should the law should be changed to allow joint tax filing only when claiming dependent children?
Personally I think there should be no deductions for children and everyone should file an income tax return singly.
Lower the tax rate for everyone and get rid of all deductions and tax credits.
Keep It Simple Stupid.
Would you subject all income to this tax?