Question

why asteriods not rotate?

Answer 1

Asteroids and comets rotate, but not exactly like the Earth. Because Earth is a sphere, its mass is distributed relatively evenly, so it rotates smoothly.

Answer 2

Asteroids are sized about 100 feet to 50 km even, are present in our solar system.

They rotate but not uniformly around the Sun in elliptic orbits.
 
There are some asteroids rotating non uniformly around some planets too.  Some asteroids rotate around another too.