It seems pretty common sense that the main things people want to convey in medical emergencies where they're unconscious or their identity is unknown are allergies and reactions, hence why we have medical allergy bracelets and similar things.

If it's life and death and I'm unconscious, it's unlikely they would be able to access my medical records regardless, given the state of healthcare data interoperability (I have a lot of experience in this area). If I am conscious, I can tell them where to get my records, whether they're in Random Hospital X's database, or my personal DB.

I tend to agree that in the average case there's no real downside to doctors not having my medical history.