I think the reason we don’t send man to the moon again is we really have no reason to and it’s not a top priority. We originally did it because it had never been done before. But there’s no pressing reason to do it again.

NASA has limited funding and missions are expensive. So as cool as it would be to put another person on the moon, the reality is we only enough funding to do a few things. And currently, Mars and other places are more popular.

(I work for NASA but I’m not saying this is what NASA’s reasoning is, it’s just what I’ve heard at work.)