A lot of undocumented citizens are not in the country by choice. They were brought here at a young age by their undocumented parents. These kids have grown up with an American cultural identity and not even much of an understanding of where they came from. Charging thise kids more for college is unfair to them.
If undocumented immigrants want to attend college, they need to first get out of the country, enter it legally, and jump through all the hoops LEGAL immigrants jump through, including paying some hefty fees. Then if they want to go to college, they can, and they of course should pay the same rate.