WHY don't Moons have Moons!

All  the planets of our solar system , except Mercury and Venus have their own natural satellite - MOON. Although astronomers have spotted some asteroids with moons , the planet's strong attraction force called as gravitational force would make it difficult for the moon to keep control of its own satellites . To prevent this , there should be a vast space between the moon and the planet so that the moon would escape from the force of gravity of the planet  or the planet's gravitational force would be negligible for the moon . Orbiting far from its parent planet , a relatively massive moon might be able to  hold on its own moon . 

Even if we spot a moon with a moon , it probably won't last long because tidal forces from the parent planet would tend , overtime , to destabilize the orbit of the moon's moon ; eventually pulling it out of orbit.

"A MOON'S MOON WILL TEND TO BE A SHORT-LIVED PHENOMENON!"