Here's why:

* Moon phases: The moon's phases are caused by the changing angles of sunlight reflecting off its surface as it orbits Earth.

* Full moon: A full moon occurs when the entire sunlit side of the moon faces Earth.

* Daytime: During the day, the sun's light is much stronger, making it difficult to see the moon.

* Moon's position: A full moon is typically opposite the sun in the sky. This means that when the sun is up (daytime), the full moon is on the other side of the Earth, hidden from view.

You might see other phases of the moon during the day, like a crescent moon, but a full moon is only visible at night.