Well in Israel we have what we called a "Kodan", basically an extra anti-theft mechanism hardwired to the battery of the car. You need to put a 4 or 6 digit code in order to be able to start the car, this "Kodan" gives you the option to try for ignition ONLY, then the key fob needs to be present in order to START the car. So for example if you don't put the code properly and have the key fob, the car will never start.
So even if hypothetically I would leave my key fob inside the car I would not be worried since they need to overpass that system first. Is it possible to override the system? Of course it is, but also... Why the hell would I leave my key fob in my car in the first place!? My key fob will always be in my pocket and nowhere else.