I think the benefit of this is that other people can't easily see what you posted. For example recruiters for jobs, journalists or activists trying to publicly

I think the benefit of this is that other people can't easily see what you posted. For example recruiters for jobs, journalists or activists trying to publicly doxx or embarrass you, stalkers, people with a grudge against you, etc. If FB has this data squirrelled away somewhere in cold storage then in order for anyone to harm you with it, FB has to admit to keeping it (which would be a scandal) and it has to get out into the wild. That is a reduction in risk compared to someone just looking at your profile.