Here's why:

* Gravity: Stars are incredibly massive, meaning they have a strong gravitational pull. This pull attracts smaller objects, like planets, and keeps them in orbit.

* Formation: Planets are formed from the same disk of gas and dust that surrounds a newborn star. As the disk rotates, material clumps together, eventually forming planets that inherit the star's rotation.

There are exceptions:

* Rogue Planets: Some planets are ejected from their star systems and wander through space without orbiting a star.

* Binary Star Systems: Planets can orbit two stars at once in a binary star system.

But for the most part, planets orbit stars because of the fundamental force of gravity and the way planetary systems form.