It's irrelevant whether you use an acronym such as P.O.M (Prepare, Observe, Move) or if you just use 1,2,3. as a sequence of events before moving off.
What is important is that you check it is safe before you move off.

Having entered your car, carried out the Cockpit drill to set yourself and mirrors up etc, it's now time to consider moving off.
You start the engine, place the car into 1st gear and get moving.
But were totally unaware of your surroundings.

THIS PUTS YOU AND ANY OTHER ROAD USER AT RISK!

How long would it actually take you to look over your left shoulder,
look in the left door mirror,
look ahead,
look in the interior rear view mirror,
look in your right door mirror,
and then finally over your right shoulder?

Literally seconds to carry out this simple check to see if moving off would cause you to interfere with someone else.

It's not hard to do, it takes seconds, but it might just save your life or someone else's.

What it will 100% do is cause you to fail your driving test by NOT DOING IT!

As a pedestrian you wouldn't walk out into a road to cross it without looking......would you?

If you wouldn't do it as a pedestrian, why would you think it's safe to do it just because you have a metal box around you?

That metal box is just another means of taking you from one place to the next, it's not a life saver.
And that fact that it is metal and weighs on average about 1 tonne form the most basic of cars, it can do one hell of a lot of damage, especially to pedestrians, cyclists, motorcyclists and horses and riders. Not to mention what would happen if another vehicle weighing 1 tonne or more were to come into the path of your vehicle because you didn't bother to look!

Think about it!