Why DMARC failure (forensic) reports are not supported by major ISPs such as Google, Microsoft, Yahoo, etc.?

DMARC failure (forensic) reports are not supported by major ISPs such as Google, Microsoft, and Yahoo because these reports contain Personally Identifiable Information (PII). Specifically, these reports include details like the "From" address, "To" address, subject line, and the email header. Sharing this level of detailed information raises privacy concerns and potential legal issues, leading ISPs to avoid supporting forensic reports to protect user privacy.