The information has at least two purposes:

For field providers, your name, age, meds, allergies and medical history are generally most important. From my perspective, as field provider, if you are unconscious / unresponsive, I will be treating your immediate life threatening condition(s), while it is nice to know the above information, it is not absolutely essential. Knowing your meds and medical history may or may not steer my priorities, but I am going to treat you, the patient and your current medical emergency. Knowing you are an insulin dependant diabetic may nudge me to check your blood glucose levels sooner, than if you are taking calcium channel blocker, where your signs and symptoms warrant me to consider cardiac emergencies as a priority.

In addition to the information above, the hospital most likely will benefit from the additional information such as contacts, SS#, insurance provider, doctors, etc. which may be needed to expand upon the treatment and for accounting applications.

Pete