Exomining, off-world energy and goods production. Long term studies of planets. Setting the stage for humans to become an interplanetary species. Discovery. Adventure.
This I agree with as my SF, science and 'what's over there where the sun sets' side of me loves it. However another part of me thinks...
...where the funds to kickstart this grand adventure will actually come from, or what amazing out of the blue technologies make it much more cost effective, I don't know. Right now neither funds nor technology is up to scratch. The world today would have to invest a huge part of its wealth to do this....I'm not saying that everything is economic but if you destroy the world's economy just to get a small colony on Mars (that will fail because Earth won't be able to supply it with anything anyway if it's going through disruption....) then that's just not going to happen.
Sure landing a team of astronauts or taikonaut for a one-shot
is probably in our grasp (and probably cheap enough!) and would be be highly impressive and, like the moon-landings of 1969, a milestone in humanities history. But it'll be a one-shot that does not stand replication easily.
1. People already live in miserable, inhospitable places on earth, now - those in the far north, those in the desert, those in malaria infested jungles, those on oilrigs - environments that although habitable are still extremely hostile to human life.
The environments you mention do have people living in them. Are they miserable? Probably not, otherwise they'd be empty. Oil rigs are closest to space travel, but then it's all for a pay packet, getting something out of the ground and you know you are only a helicopter ride back to the mainland. Try replicating that in deep space beyond the moon orbit. Nope, not the same.
Also calling these places 'extremely hostile' to human life is a bit too much IMO. These places all have atmospheres with oxygen, shielding from solar and cosmic radiation, temperatures that are easily dealt with, and a thriving biosphere. Places that don't have that i.e. Mars, Moon - yeah that's a bit more 'extreme' in my book.
2. Society doesn't have to be as it is now.... It can be conducted for the good of all,
Oh you sweet spring child!
Well, we need our optimists as well as our pessimists, I suppose. Give us a well-thought out path to get to a society for the good of all and I'll join you. I'm just looking at about 5000 years of human history and I am not totally convinced!
3. Glass half-empty cynicism can as bad as gee-whiz sci fi. People predicted all kinds of awfulness for 2024 and none of it has come to pass as envisaged. The new whaddyacallit - paradigm - has positives and negatives of its own and the future will no doubt be the same but different. We can at least try for these things and maybe, like the space race of the 60's, great technological boons will fall out that can help us all even if we don't achieve man on mars.
No idea what all kinds of awfulness were predicted for 2024. Personally I did not hear of any. Nothing either good or bad comes to pass as envisaged anyway so I don't like this sort of argument.
The space race of the 1960s was not a great technological boom. It was exciting. But, for example, one real boom that changed the world - the advent of solid state computing and its subsequent explosion that continues to this day - was happening and would have still continued as it had if the US went to the Moon or not.
At some point the economics/risks-reward/"technological ease" will (hopefully) reach a point where it starts to make sense. Although I would still think we ignore Mars and focus on building bigger and better O'Neil cylinders and all sorts of much better space habitats (that we can then send as spacecraft to all sorts of places around the Solar System - why not take home with you when exploring, rather than trying to make a home in some frozen moon billions of miles away from help?)