Why has no human stepped foot on the moon for 50+ years? This never made sense to me.
Technically, this is not true. Unfortunately, it will be true in a few weeks.
The moon is a bit of a luxury. We're going back because it has gotten a lot cheaper to do so (and China is going for it soon, which spurred the US to go back before China gets there). The sole reason the US is more recently in such a hurry to go back is because of China's progress.
There is very little value in merely going back and walking around again. The only good reason to go back is to begin building a long-term settlement/base of some manner, and we couldn't afford to hope to attempt it until recently. Starship is the only thing that can make that economically viable this decade.
Why haven't we gone back to the moon? Funding dried up real quick once it was clear the Space Race could be won with the existing amount of money spent, new projects had to answer "why" in a concrete way to compete for limited resources and it was not at all clear what we'd go to the moon for compared to, say, building the ISS.
Space theorists in the 30s - 50s assumed that you would have to build up on-orbit Earth infrastructure before the moon could be sustainably reached, meaning you could go back whenever just because. That is, you need stable communication, transit hubs, refueling, space-based construction went the thinking. Both the US and the Soviets took big, expensive shortcuts in the Space Race but I find it hard to believe that the original analysis -- space is only as reachable as its infrastructure allows -- hasn't been showed true in the last 50 years.
https://www.universetoday.com/115672/you-could-fit-all-the-p...
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Actual serious answer: It takes a lot of energy to get to the moon. Even more to land safely. Even more to take off again. Even more get back to Earth.
That energy costs a lot of money. It costs a lot more money to test all the things that use that energy. We are at the bottom of an energy and money hole, the moon is at the top.
The focus (pun intended) has been space based telescopes and study of more distant planets and objects.