That person is fucked when they lose their phone anyway, because they're also the sort of person who has never backed up all their photos/contacts/iCloud files anywhere that doesn't require iCloud auth to get at. At some point we have to either properly educate people on the fact that they need to have a recovery path, or we have to accept that they're going to need to rebuild their entire digital life every 2-3 years.

This is your cue to go get your parents to add you as recovery contacts for their Apple account now, rather than finding out that exists when they lose their phone.