The kits were initially developed when it became apparent that medical help was available on board, but too often drugs needed were not.

The med kit is based on the experience that the vast majority of flights have someone on board who has some medical experience, nurse, doctor, NP, PA, EMT, paramedic, other first responders, etc. First thing is the announce on the PA seeking such folks. Been on flights when that happens and each time there's more than one and the most appropriate is selected to work the patient. That's who assess the patient and, if needed, will administer drugs and decide if an emergency landing at the nearest city or town is needed. Fallback is the Flight Attendants who are well trained in the most likely issues and when and when not to intervene.