Here's why:

* Rotation: Saturn rotates very quickly, which causes it to bulge at the equator and flatten at the poles. This is similar to how spinning a ball of dough makes it flatten.

* Gravity: The strong gravitational pull of Saturn pulls everything towards the center, creating a sphere.

* Gas Giant: Saturn is a gas giant, meaning it's made of gas and not solid rock. This makes it more susceptible to deformation from rotation.

So, while Saturn is not a perfect sphere, it's much closer to that shape than a pear.