How do I know that, you will handle my passport data with care? Banks I can trust(despite numerous leaks), you as a random social media or online service with zero regulation, I won’t. Plus this opens up immense ways to sue you for collecting unnecessary data and personal information, unless you are massive and have an army or lawyer or have a KYC requirement.
I plan to outline exactly what data I store. I don't plan to store raw passport number/name details, rather a hash so I can verify the same passport isn't used twice.
So even if the DB leaks no one (except the government) will be able to tie your real life identity to the account.