Some schools require FAFSA (and possibly verification) for merit scholarships. Bizarre but true. Check with the school to see if they do.
Some states give modest grants to instate applicants for things like GPA, regardless of income, but you have to file FAFSA to get it.
If you want to take out a federal student loan (~$6000/year max), then you need to do FAFSA and any requested verification.
If none of these situations apply to you, then you can ask your application to be considered without aid. Call the school and they can change it. Otherwise they will be looking for FAFSA and any requested verification.