system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why aren't our pupils always dilated so that we see more all the time?
gpt
Stare into a bright light. How much can you see?

When your pupils dilate it is to allow more light into your eyes. Letting in more light in dark situations helps you see better, but letting in more light in a bright situation makes it harder to see and can damage your eyes.