I carry 2 sets of keys at all times.......and still have one hidden on the vehicle. I got into the habit of 2 sets of keys when working as a commercial carpenter and carrying lotsa tools and materials. It didn't take too many times of sending a helper to get something out of my van and have them forget to give my keys back. Not fun at quitting time when they drive off with your keys....:mmph:. Or....if many trips were expected during the day I would have them hold my keys.......if I forgot to get them back at the end of the day I was not stranded.
My oldest son was horrible about locking his keys in his van....I carried a spare key for him......:smile:.
I listen to the fire scanner........it's not uncommon to hear "Keys locked in vehicle". The fire dept won't always break your window....:lol:. They have their ways of opening your vehicle in a non-damaging way. Two of my sons are firefighters......they don't mind going for a ride. Don't think of it as wasting resources......these trucks do need to be run on a regular basis. That's why you see firefighters going to the grocery store, for the day's food, in an engine or ladder truck.