An adult whose parents don't have assets gets student aid, but an adult whose parents have assets doesn't get student aid because that adult student's parents have assets to presumably pay for his/her college education?
There is no legal obligation for the parents to exhaust their assets to pay for an adult child's college education. Pretty much every state's law provides that the financial obligation of the parents end when a child reaches the age of majority, 18 years old.
So, why should the adult child in the one scenario be denied student aid and the other receive it?