WHY are planets, satellites, and stars round while asteroid…

WHY are planets, satellites, and stars round while asteroids are not?

Small asteroids have too weak gravity to deform rocks, so objects up to a few hundred kilometers in size have an irregular shape.

The matter of a star or planet tends to be at the same distance from its own center of gravity. The reason here is the same as why the water in a pond is set at the same level, rather than rising with a hump.