Some people have chronically bad short-term memory, such as myself. It's not a matter of responsibility, or lack thereof, that makes people forget. Stress, brain injury, or simply being interrupted at the wrong moment can make people forget basically anything. Like taking your kid out of the car baby seat and handing over to daycare before driving off to work and parking the car in the sun all day long.
Myself I can forget most anything; not keys or wallet thankfully (so far anyway); I am rather firmly attached to those - as am I to my head or else I'd probably lost that too somewhere, more than once most likely. I've forgotten loads of other stuff however, a Polar exercise watch at the gym and multiple gym pants too, a nice leather backpack from Crete on a tram, multiple umbrellas...
If I don't forget stuff when I'm out, I forget them at home. Like back when you paid your bills in person at the bank or post office, you go into the city to do your monthly errands and all your bills stayed behind even though you put them right next to your friggin shoes so you'd absolutely remember to bring them? Yup, that was me. 😛
You use the same fob to lock the front door to your home too, or do you lock the door from the inside, then squeeze your way out through the cat flap?