Here's a classic letter by Ernst Stuhlinger to Sister Mary Jucunda, a nun who worked among the starving children of Kabwe, Zambia, in Africa, who questioned the value of space exploration:
It seems telling that the most concrete example he gives for the value of human space flight is the usefulness of unmanned satellites.
Simplistically it's true that whenever you spend money on some effort there's going to be some benefit. Paying NASA scientists to dig ditches would have some benefit in stimulating the economy, even if it doesn't offset the costs (material and opportunity). Would it be the best use of resources, however?
Whenever I go down the rabbit hole of "spinoff technologies," I find a lot of it to be a gish gallop of stuff, much of which is overstated. There's a reason why you hear NASA talking up pioneering research done on Alzheimer's at the international space station, but you don't read Alzheimer's researchers talking about breakthroughs coming from the ISS.
Still, there are a lot of important technology that NASA has been involved with. But when you look into most of it, the connection to human spaceflight is tangential at best, and often completely non-existent (NASA does a lot of stuff outside of human spaceflight).
The kernel of the argument is accurate - scientific research can be important even if it doesn't provide immediate dividends. But too often people misuse that to argue that no amount of money is poorly spent. It's precisely because scientific research is important that we need to carefully consider the return on different projects, and make sure that the funds that are being allocated are well spent.
Honestly I think all the side-effect technologies are just marketing. The true goal of space exploration is and should be to turn us into an interplanetary and eventually interstellar species. Yes we don't have the tech to do all of that just yet, and maybe some new physics is required, but just as Cathedrals were intentionally built over centuries we should intentionally build out the capability to the best of our abilities. Not only is it essential to our long-term survival as a species, it would provide a cultural release valve just like the old frontier, only this time no natives to worry about.
I highly doubt much if any of the space exploration now is going to have a significant impact on humans being an interplanetary or interstellar species. A good analog might be the heroic age of Antarctic exploration. It was interesting, but it Amundsen's expedition never left we'd be in the exact same place we are now when it comes to exploring Antarctica.
If 200 years ago a country had decided to keep a settlement going at the top of Mount Everest in the name of progress, it wouldn't have been any benefit to the modern efforts to keep people in the ISS. Likewise, I don't expect the ISS to have any noticeable impact on efforts to have people live on other planets.
Keep in mind, this doesn't mean we won't make progress. A lot of people are excited about what SpaceX has been doing, and until very recently they've been entirely involved in non-human cargo. There are a lot of reasons to send things into space, which is why we send up a lot of stuff. There's just not many reasons to send people up at the moment, other than to be able to say we're sending people up.
We have to start somewhere, and private industry isn't going to start it because, as you point out, there's not many reasons to do it at the moment. The ISS is allowing us to experiment with living in orbit for extended periods. We certainly have to master those relatively simple conditions before attempting to survive a manned trip to Mars or living on the Moon.
Also SpaceX wouldn't exist without the ISS. It's NASA contracts for resupplying the ISS that kept it alive in the early days. Which just goes to prove the model: Government invests in "useless" project that allows private industry the toe-hold of capital needed to kickstart a new technology.
To your Antarctic exploration analogy, I'd say the ISS is more equivalent to McMurdo station than the Amundsen expedition
In 2012, William Doino Jr, wrote that "The remarkable thing about Hell's Angel is that it purports to defend the poor against Mother Teresa's supposed exploitation of them, while never actually interviewing any on screen. Not a single person cared for by the Missionaries speaks on camera. Was this because they had a far higher opinion of Blessed Teresa than Hitchens would permit in his film? Avoiding the people at the heart of Teresa's ministry, Hitchens posed for the camera and let roll a series of ad hominem attacks and unsubstantiated accusations, as uninformed as they were cruel."
I afraid we stray from the topic, but yes, i'm not either one for Hitchen's obvious ideology-based vendetta against Catholicism in general and Mother Teresa in particular. Having witnessed first hand the Sisters of Mercy at work in rural Africa where no-one except these proselytes of Mother Teresa thought it worthwhile to take in orphans, lepers, old people without relatives and give them food, shelter, life in fact. Not an atheist in sight.
It's laughable that Mother Teresa's critics try to disparage her by contrasting the care of her organization vs. that of a western hospital. The reality of the situation was that you either passed away in a soft bed with someone by your side or alone on the side of the curb. I know which one I would prefer
"Why Explore Space? A 1970 Letter to a Nun in Africa" - https://launiusr.wordpress.com/2012/02/08/why-explore-space-...