It’s not like every problem in space is running out of oxygen in 90 minutes. I can imagine plenty of scenarios where having additional resources in the matter of days vs months would make the difference in a life or death scenario. Especially if we were able to establish a decent support network on the ISS or other space stations.

Not to mention you would be able to realistically cycle out astronauts on a moon base, whereas being assigned to a mars base would be a one way trip for many.