You may need to stop somewhere on the side of the road due to one or the other reason. Several countries mandate that you need to turn in your sidelights so that incoming vehicles can know that you have stopped at one place.
For this purpose, you need a properly charged battery. More so, if your parking light bulbs are old and worn out, you need to get them replaced with the new ones timely. Fluorescent parking lights last longer than incandescent bulb lights.