We cannot see a full moon every day because the moon's position relative to the Earth and the Sun changes throughout its orbit. The moon orbits the Earth in an elliptical path, completing one orbit in approximately 27.3 days. During this time, the moon goes through different phases, including the full moon phase.
The full moon phase occurs when the moon is positioned directly opposite the Sun from our vantage point on Earth. In this configuration, the entire illuminated side of the moon is facing us, making it appear as a complete circle of light.
However, as the moon continues its orbit around the Earth, the angle between the moon, Earth, and Sun changes. This means that the sunlight falling on the moon will illuminate different portions of its surface, causing different phases to be visible from Earth. The changing angles result in the moon appearing as a waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning crescent over the course of a month.
So, while we do experience a full moon approximately once a month, we cannot see it every day because the moon's position and phase are in constant motion relative to the Earth and the Sun.