Automatic cars require P speed when ignition, so it's not a big deal. Speed P is the parking speed. This speed is used when the car is stopped and the engine is off. If you do not change gear P before stopping and turning off the engine, the car will not be able to shut down normally. If speed P is not engaged when starting the engine, it will not start.
Automatic cars have a P speed and an N speed. Both P and N speeds can be used when parking, but there is a difference between these two speeds.
After shifting into gear P, the automatic transmission locking mechanism can lock the transmission gears, which is equivalent to indirectly locking the wheels.
After shifting into gear P, it cannot move even if the handbrake is not applied.
However, there is no locking mechanism forr lock the gearbox speed after shifting to speed n. If the handbrake is not applied at this time, it may be moved.