While "as safe as possible" is certainly the goal, most of the research is centered around first clearing the low bar of "safe enough to even make it there and then do some science". "Earlier death" might mean "on the way to mars", which would end up being a much bigger waste of money and effort (to say nothing of the political capital). Those are the questions we're trying to answer right now.

The other side of these things is that the research being done is not single-purpose. The lunar missions were an amazing human achievement, but their lasting legacy can be seen much more clearly on earth. Our radiation work has homeworld implications for understanding radiotherapy. Heavy ion therapy is a rapidly emerging technology that has the potential to make some previously-mortal cancers tractable, and understanding its full biological effects is critical. By exploring new worlds, we hope to be able to improve the lives on our own as well.