Earlier quoted context omitted.
>when automatic transmissions are consistently outperforming humans at fuel efficiency Do you have data to back this up? Unless you're driving a dual clutch "dry" transmission or a CVT, because of Physics, an automatic transmission will always be less efficient. The Automatic transmission Torque converter [1] will waste some of the energy provided by the engine, especially with city driving. Also, most automatic cars…
Coasting in neutral or with the clutch disengaged is both more dangerous and less efficient then engine braking. In the UK you will fail your driving test if you coast, and in some countries / states it is illegal - with good reason. Just google it - not a single article supporting your argument.
Understandably it is dangerous as you are not in control of the transmission and therefore the wheels, hence the failure in the UK. But I got through some incredibly scarce times by coasting a bit on the commute to work...
With automatics you would need to brake down the hill to stop the car "running away" as it wouldn't engine brake automatically to compensate for gravity's effect.