The point is that we don't have technology (or at least not proven) to make a habitat on earth that can reliably provide isolation from harsh atmosphere.

When you are sending people to space on an experimental rocket, with experimental supply for an experimental habitat, all of that shit better be engineered to a huge safety factor, because its not a matter of if things will go wrong, its how often will they go wrong and what the impact will be. To deal with that kind of unknown requires a level of technology that should make it possible to live in Antarctica for extended period of time without any external shipments coming in to resupply. That means heating, oxygen generation, food resources, air filtration, full medical bay capable of advanced surgery, and a bunch of other smaller things that all matter in the end.