A Simple Question
What do you think has changed? Moving out into the solar system was the next step most had in mind back then. The Moon is a dead end for colonization unless a commercial use can be found for it profitable enough to pay for the supplies that will forever need to be shipped there as opposed to produced there as they could be on Mars. It has appeal as a research base, but that is just as limited a role as Antarctica currently plays in the future of mankind.
Regards,
Mark