Antarctica IS inhabited (for my definition of "inhabited").
Perhaps the first bases on the Moon and Mars will be small Antarctic-like ones, from every big country on Earth. Perhaps Mars will never be "terraformed", instead the enclosed bases will slowly expand to accommodate expanding populations. Some people on Earth already live totally indoors, and in the future, many Asian cities in polluted environments may have roofs outside, as well as inside, to keep the air clean.
Fast transportation, as needed by most humans, has very little to do with current space programs, most of which use extremely expensive and mostly single-use systems.
Again - there is no real need, right now, to live on Mars, absolutely. Neither is there a real need to live on ISS. Still we are doing it.
Perhaps the first bases on the Moon and Mars will be small Antarctic-like ones, from every big country on Earth. Perhaps Mars will never be "terraformed", instead the enclosed bases will slowly expand to accommodate expanding populations. Some people on Earth already live totally indoors, and in the future, many Asian cities in polluted environments may have roofs outside, as well as inside, to keep the air clean.