Here is why an FOIA request would either be denied or so heavily redacted as to be useless -

Exemption 4 – Protects trade secrets and commercial or financial information which could harm the competitive posture or business interests of a company.

Exemption 5 – Protects the integrity of the deliberative or policy-making processes within the agency by exempting from mandatory disclosure opinion, conclusions, and recommendations included within inter-agency or intra-agency memoranda or letters.