You can't see the outside lights on your car when you're sitting in the driver's seat. Either get out occasionally and look or have someone else check them. If you get out you can't press on the brake pedal to see if those lights work, so it's better to have someone else check.
The other day I noticed the left front parking light on the car in back of me was out. When I stopped at the next stop sign, I got out to tell the driver. Of course it was a woman and I believe she got scared as she starting backing up. Finally, when I didn't move toward her, she stopped and rolled down her window so she could hear my screaming. Her concern was legitimate as I could have just used that excuse to get her guard down . . . to do her bodily harm. Knowing your lights are working properly could keep you out of danger.
A few months ago, at night, I noticed the left turn signal on the car ahead of me on the roadway. "What is the big deal?" you might ask. Well there were no brake lights and the car was stopped dead in the road. Luckily seeing the turning light, I was able to stop in time. He only engaged the turning light after he came to a complete stop; consequently, I had no advance warning.
Lights are not only to see better at night, but also very important is to BE SEEN, whether day or night.