Aside from scientific research (which can be mostly or entirely done remotely by machines), there is exceedingly little reason to inhabit Mars, or any other planet for that matter.
There are sociopolitical implications of extraterrestrial missions (think: space race), but in terms of human habitation at scale, what would be the point? In science fiction, there is usually a major impetus: the earth is dying, the earth was stolen by aliens, etc etc. In these cases, though, the fiction part handles most of the stuff that would be hardest in real life.
From a practical standpoint, anything that can be done on Mars can be done for mere fractions of the resources here on Earth. At some point, it just comes down to the economics. Even if there were major issues with pollution or resources shifting the planet towards uninhabitability, fixing or mitigating those problems is likely to use orders of magnitude fewer resources than going to Mars. If such problems were beyond fixing, it wouldn't mean Mars gets cheaper. It would mean humans go extinct.
Now, there are charlatans who will say we absolutely need to inhabit Mars and will give you a barrage of tenuous reasons. Musk comes to mind. Usually this is done to drive investment in companies or technologies which have been nudged into seeming Mars-adjacent, but at the end of the day, they're just raising funds for regular rich people stuff here on Earth.
A fantastic summary.
Addendum to #2: to add insult to injury, a lot of the training data in AI models was used without consent. That means that the output of skilled people was stolen from them in order to train systems designed to steal from them again.