Many Moon hoaxers demand to know "Why," if we were able to go to the Moon in 1969, "has there been no serious attempt to return to the Moon?"
Well, first of all, Apollo 11 was already the
third mission to go to the Moon, Apollo 8 and Apollo 10 having preceded it. But it was the first to land humans on the Moon. As for returning, a further six missions followed Apollo 11 to the Moon, five of which landed there.
However it's true that Apollo missions 18-20 were cancelled, and that's been the end of it.
Curious Droid explains why humans haven't walked on the Moon since the 1970s. But if you're in a hurry, the short answer is: going to the Moon was
incredibly expensive, and once the US had shown up the Russians, Congress didn't think it was worth the money, just for more science.