We are usually VERY careful with the keys to the vehicle. (It’s best to have two or more sets with you and hide one set close to the get-away vehicle.)
In some cases, it’s the difference between life and death.
… Sandra Ordner, 47, of Daphne, whose body was found last week outside her locked SUV at a North Carolina mountain parking lot, died of hypothermia hours after she told her husband she was going hiking, the local sheriff said Thursday.
Macon County, N.C., Sheriff Robert Holland said that it had been extremely cold and raining in the hours before Ordner’s body was discovered in the parking lot of the Whiteside Mountain Trail.
Ordner’s keys and cellular telephone were locked inside her 2002 Land Rover sport utility vehicle, Holland said. …
besthike.com 
Tragic. Looks like she was already hypothermic before she got to the car, otherwise she’d have likely been able to make more of an effort to break a window.
Perhaps as much a lesson about being prepared for cold weather, as carrying car keys securely.
That had not dawned on me.
How could she be so weakened as not to have picked up a rock?