People often see their smartphone before they sleep.
If you see something bright in a dark place, or a bad position, it will increase eye pressure and fatigue. As a result, you could get dry eyes, myopia, glaucoma, and blindness. There is also an article saying that blue light from somethings in the dark is not good for the eyes.

To prevent this, 'Bright Eyes' Keeper uses the built-in sensor to determine if the surroundings are dark and bring up the lock screen. Not only does the lock screen appear when the environment is dark, but you can also display the lock screen for a set amount of time. This will help your healthy lifestyle.