This is also useful when parking past the inside part of a curved road at night, where traffic from behind you might not see your car in time as they rounded the bend in the road. This is especially true if your car is dark-colored. If your left parking lamp is on, that gives them advance warning.

If you park on the correct side of the road here in North America, then you only have to use the left lamps. The right lamps are intended for use in countries where they drive on the left side of the road.

However, the right lamps can also be useful here in NA if the rear of your car is jutting out of the driveway a bit at night.