Here's why:

* Earth's Tilt: The Earth is tilted on its axis. This tilt causes different parts of the Earth to face the sun at different times of year, leading to the seasons. This tilt also affects how constellations appear in the sky.

* Circumpolar Constellations: Some constellations, called circumpolar constellations, are located near the celestial poles (north and south). Due to Earth's rotation, they appear to circle around the pole star and never set below the horizon for observers in certain hemispheres. For example, Ursa Major (Big Dipper) is circumpolar in the northern hemisphere.

* Latitude: Your location on Earth affects which constellations you can see. Constellations near the celestial poles are visible all year round in certain hemispheres, while constellations further from the poles may only be visible for part of the year.

So, while some constellations rise and set as the Earth rotates, others, like circumpolar constellations, remain visible throughout the year.