I haven't read the last 10 pages... but I saw this one.
It's actually a phase in and a phase out on the earned income tax credit. I'm just throwing random numbers out there to make a point, but it's like, if you make more than 15k, but make under 30k, then you qualify. The main reason was to have an objective way to try to weed out children from obtaining the tax credit, which could overshadow the dependent deduction.
It's also the caveat of EARNED income. Passive income does not count towards the earned income tax credit. Income from activities such as donations or panhandling are not considered 'earned'.