Why is China planning to crash a spacecraft into an asteroid at 9 km/sec?

China's CNSA is planning to crash a spacecraft into an asteroid before 2030 as a planetary defence experiment, SCMP reported. CNSA aims to directly alter an asteroid's orbit relative to Earth, or even break up its structure. The spacecraft is expected to hit the asteroid at nine kilometres/second, or about 26 times the speed of sound near sea level.