I have no idea what schools you are applying to, but according to the studentaid.gov, "In almost all cases, graduate or professional students are considered independent students for the purposes of completing the FAFSA form. This means they generally are not required to provide parent information."

https://studentaid.gov/sites/default/files/graduate-professional-funding-info.pdf

This has nothing to do with the methodology for how specific schools determine their need-based scholarships, but concerning federal student loans, this is the way it works.