On July 20, 1969, Apollo 11 put 2 men on the moon. The last humans to hit the grey rock in the sky were on Apollo 17, in 1972. It's now 2019, and we haven't gone back since. That's 47 years.

So why haven't humans stepped back on the moon?

Source: Science

At the time of the moon landings, the US was at the height of the Cold War. Once the Soviets had proven that they could put stuff in space (looking at you Sputnik 1), it was up to the Americans to flex their technological might. They had to demonstrate their status as the number one global superpower.  

So NASA was allotted immense resources - nearly $264 billion in today's dollars between 1960 and 1973. Using those kinds of resources today would be a waste, especially to prove something that's already been done.

Source: Space

During the 60s, NASA's budget was 10 times what it is today. So apart from the fact that it's been done, they also no longer have the money to carry out another manned moon mission. However, that doesn't mean it's not going to happen.

Under Project Artemis, NASA aims to establish a long-term, sustainable human presence at and around the moon by 2024.

The objective for this will be a crewed trips to Mars.

Source: Irishexaminer

So there you go - it's basically the fact that we've already been there, plus the massive amount of resources it would require along with the current political climate that's to blame for the lack of human footprints on the chaand.