Wrong? As a new driver I've never had to use keys to start a car and so I've never had to even consider taking keys with me. My fob is on my belt loop at all times. If I were put in the position where I had to use keys, I can see how it might slip my mind when I'm in a rush trying to be a productive employee and service the customer.
The only reason the driver left the keys in the truck was it was still running and he did it because it was more convenient and he new that he couldn't get in trouble with telemactics. He didn't turn the truck off and just leave the keys in it people who have to turn the ignition off automatically take the keys with them.
Your theory about to FOB is also BS even with never personal vehicle having a similar FOB most people personal vehicle still uses some sort of key and or have had to use a key to start a car in the past.