Because we have already been there, we got plenty of lunar rocks, and there is no particular reason to go back. Mars is much more interesting, and asteroids provide far better economic opportunities.
"We" have done no such thing. Only a hand full of people have been to the moon. I don't know about you, for all I know you might have been one of them. I do know that one of them wasn't "me."
That is the most important reason I want to go back to the moon. I haven't been there and I would love see the original sites of the first moon landings.
That is how I want to do it, tour the moon like tourist.