Why Haven't We Been Back to the Moon?

Why haven't we been back to the moon? Is it time for another manned exploration of this wonderous place? I think so. 

Man has not stepped foot on the moon since 1972, despite initial dreams of moon bases and lunar colonies. The development of such things would be a costly and timely endeavour, but some researchers belive it would be a fruitful one. A paper was recently submitted to the journal of Planetary and Space Science by researchers from the UK, Germany and The Netherlands, outlining the scientific importance and possible benefits of future lunar surface missions. The Moon is an important element of our planet, and there is much still to be investigated about the relationship between the Moon and Earth. Moon exploration would also give us new information about the possible workings of other rocky planets in our solar system. 

So why haven't we been back after all this time? Perhaps there is something scientists aren't telling us about the things they found on the moon..

Conspiracy theories are always fun.

What do you think?