If we can't manage to keep Earth's ecosystem thriving to support us, we certainly won't be able to create a new self-sustaining ecosystem elsewhere. And without that, there's no chance of any non-Earth settlement being able to sustain a healthy human society and culture long-term.
Without some serious (currently impossible) terraforming, Mars colonies are limited to deep caves or heavily shielded buildings, no outside to relax, nowhere else to go. Have a look at the list of crimes in Antarctica, a similar situation where people are stuck together, that's not a good environment for mental health, and it will be worse farther away. A Mars colony (edit: or space station) owned by a private company will be a corporate prison, the inhabitants are 100% dependent on that company - who would voluntarily put their lives into the hands of the whims of some narcissistic hoarder with no empathy or regard for workers?
My point was more or less the opposite: Anyone interested in space exploration should also be interested in keeping Earth well livable, because that is needed for its success.