It's a hard problem. Many students have very low income on paper, but also have options that poor non-students don't. There's low-cost housing available only to students. There's parental money - not for all, certainly wasn't for me personally, but for many. There's student loans. It would be unfair to those poor non-students to use the same classification for students based only on their paper income. The exclusions that exist might be imperfect, but they also close loopholes that would defeat the whole purpose of ensuring availability of housing for low-income people in general.