The vast majority of people who get out and jog, or walk or go out on bikes, don't carry ID. Whilst this is not a problem, when accidents, or heart attacks occur, it CAN become a problem for hospital staff, police etc to identify them, and notify relatives.
It happens daily in Australia.
Recently, a lady on my Facebook page about her husband that had been injured in a motorbike crash, unfortunately he didn't have emergency contact ID on him. Sadly, he passed away hours later without her knowing.
In most cases, they will be carrying their house or car keys with them.
It's simple to just clip on an I.C.Emergency usb to their keys, and IF something happens, emergency/family contacts can be notified quickly.