Because capitalists, by definition, exploit others in order to turn a profit. Capitalism isn't a win-win game. Nothing 'trickles down'. Without sufficient government regulation, you get things like one trip to the ER bankrupting a person, Amazon delivery drivers defecating in baggies while working, megacorps like Walmart putting thousands of small shops out of business without creating anything of better value, to name just a few consequences.

The cherry on top is that the growth mindset at the center of modern capitalism (fueled by industrialism) is extremely unsustainable, due to capitalists' myopic decisions and the relevant economics' inability (or unwillingness) to calculate environmental costs as part of the profit equation. Sure, a couple centuries of explosive growth and innovation is cool, but tragically pointless when the system collapses under its own weight after it exhausts all reasonably-extractable resources. And no, space mining is not going to save it. Even oil is already becoming unprofitable to extract in many areas on our own planet, how do you expect anything involving spaceflight to be? Even events like this Branson party wouldn't exist if the companies involved didn't believe they were turning a profit (in this case, by fleecing would-be space travelers).