1) It was principally a national pride competition between the US and USSR so when the US succeeded there wasn't much of a reason to go there. We gathered loads of rocks for all the science we could want to do for a long time (they're still cracking open fresh samples to this day).
2) There's not that much economically or scientifically on the moon to really investigate that needs people there we can get new data pretty simply through orbiters or rovers
3) NASA's budget is much smaller portion of the overall budget and it's no longer singularly dedicated to the Moon
4) Longer term stays are much more intensive on resources than the short sprint to the Moon and back done by Apollo. The main goal of the moon now is to use it as a stepping stone to test for a Mars mission.
Now we're going back with a plan. Not just to win the space race, but to start laying the foundation for a permanent moon base that we can use as a way point for going to Mars.
The financial woes of the 70's combined with the substantial cost overruns of the Shuttle Craft killed Congress' appetite for further investment. Modern technology has substantially lowered the costs so we've revived the idea.
We did it last time in a lot less time taking far more risks. I think the majority is the lack of political or economic incentives, but there is something to the idea that our current culture is much more risk averse, and probably less good at "just make it work" projects than it used to be.
I think the riskiness is definitely another part of it, though if the will to do it were there I think we could still accept it now. We're definitely moving slowly in part because there's just not a huge reason to go beyond exploration.
1) It was principally a national pride competition between the US and USSR so when the US succeeded there wasn't much of a reason to go there. We gathered loads of rocks for all the science we could want to do for a long time (they're still cracking open fresh samples to this day).
2) There's not that much economically or scientifically on the moon to really investigate that needs people there we can get new data pretty simply through orbiters or rovers
3) NASA's budget is much smaller portion of the overall budget and it's no longer singularly dedicated to the Moon
4) Longer term stays are much more intensive on resources than the short sprint to the Moon and back done by Apollo. The main goal of the moon now is to use it as a stepping stone to test for a Mars mission.