Why can't humans breathe when they immigrate to the moon?

The moon has no atmosphere, and it is impossible for human beings to create the atmosphere of the moon under the condition that there are congenital defects caused by the congenital defects of the moon. The mass of the moon is very small, which makes the escape speed of the moon very small, only 2.4 kilometers per second. In this way, the velocity of gas molecules on the surface of the moon can easily exceed this value when doing thermal motion. Once this value is exceeded, gas molecules may escape from the moon forever. So it is difficult to provide air.