Imagine cobbling five different jobs together to make ends meet, but you still are ineligible for the full child tax credit! In general, tax credits that penalize the lowest wage earners are designed to encourage people to work harder. Seriously, does anyone truly believe that someone who works five jobs is not working hard enough?
The chances are high that you do not even know anyone who earns $400,000 dollars per year, never mind earn that yourself. Perhaps your medical doctor. maybe your Lawyer. The point here is that very few people actually earn $400,000 per year.