A wish from a customer, they sometimes do not have a trusted root CA or an incomplete certificate chain or CRL problems but would still like to encrypt even though it might be less secure.
This usually results in them sending out information they would like to have encrypted, unencrypted as it is not possible in the GnuPG UIs to show a warning (like we do for untrusted OpenPGP certs) and encrypt anyway. This creates a bad user experience so I tend to agree with this customer wish.
Perfect solution would be some "Trust on first use / direct trust" style "I want to trust this leaf certificate and nothing else" which might also be a solution for the current "User Trustlist" which is not denied by default in GnuPG VSD.