[nickik]

Thats not the reason. The reason is that the leaders of Earth have political constraints that does not allow them to do or change much. It has little to do with technical details.

Musk talks about it because he does not have those constraints.

As for radiation shielding, this has been a topic since the 60s. We know more or less what the risks are, we know the fundamental way to deal with the different type of radiation. The question is how to integrate it in your mission architecture.

He does not spend much talking about this because its not the fundamentally hardest problem that is to solve. The Core Problem to solve is the Transportation Problem. From what he has said about it, he proposed fundamentally the same basic ideas that people have been discussing for many years, and those should work.