It could probably be disabled, but the it's really not worth the time or effort.
If you're coming at it from the point of view of it being a pain in the **** to keep remembering to do it, just keep doing it, the neural pathways will connect, the habit will form, and inside of a month you won't even think about it. That's the power neural elasticity. Repeated tasks are relegated to the subconscious, so you no longer think about how to do them, much like the act of driving itself.
If you like to be able to start your car without getting in it and then leave it running, this too is a habit, but one that should be broken. It's bad for the car, it's bad for the environment, and it's bad for your insurance. If someone jumps in and takes the car, you will get precisely £0.00 from your insurance company.