Eventually we will run out of space for our growing population on Earth. Having a livable colony on the moon would create housing for the world's growing population. If we make the moon livable we could potentially cultivate the land and increase food production. The moon may even contain great mineral resources! The moon would also be a great tourist destination.
Creating a colony on the moon will also be good practice for when we will need to colonize other planets due to Earth becoming uninhabitable.
Also, having a colony on the moon is cool! Children dream of this stuff and you don't want to crush children's dreams, do you!?