I can tell you, right or wrong, that one of the arguments in favor of this involves situations where children are moved to the United States at a young age. Under at least some of the laws the undocumented citizen must have attended high school and lived for X number of years in the States. Hypothetically, this person could graduate high school only to realize that they are not the documented citizen they thought they were. Essentially, you are punishing the child for the parent's mistakes, something which is highly uncommon (if not non-existent) in our legal system. Also, at least in the state I'm familiar with, it is a highly uncommon occurence. Anyway, just putting it out there.