America went to the moon, because if they didn't then the Soviet would be there first. That's the real reason, and that explains why nobody ever went back since. (Why bother, when you are not number one? It's hard to justify the bills when you show it to people.)

I believe eventually we will be on the moon again, and on Mars, but it will require a lot more technical progress before the cost-benefit analysis makes sense. Or maybe all we need is a second cold war, with murderous dictators propped up around the world, CIA toppling governments, proxy wars killing millions, that kind of thing. Choose your pick.