I have a feeling this will just be ignored or buried since it sounds alarmist (and I wrote it, and I'm not a popular person), but I am going to try to explain anyway.
Its a really old story. There are lots of nuclear weapons. It seems that generally speaking, people are incredibly unlikely to use them. However, there are lots of nuclear weapons. As far as I know, it is still _possible_ for them to be used at some point in the future. There is a possibility that the use of nuclear weapons could result in nuclear holocaust. So, it seems there is a non-zero risk of nuclear holocaust.
Since efforts to reduce nuclear arsenals have not been very successful so far, it seems logical to have another plan in progress. The other option is to move some of the population off of the planet in order to avoid extinction if there is a nuclear war. Again, I admit, it does not seem to necessarily be extremely likely. But the possibility can't be eliminated, and since its such a bad outcome, it seems like, to be safe from extinction, we should have some people on another planet.
So there are two popular destination ideas: the moon and Mars. It seems obvious that one would practice by iterating with bases on the moon and then move on to Mars.
It also seems obvious to me that this should be a priority, at least for some segment of the population. And, since it is a planetary risk and probably the most challenging task ever attempted by humankind, it should be a global mission with coordination across borders.
Why isn't this a thing?