They're doing it to produce goods that people want at the absolute minimal price possible.
And there are portions of people in our society that will pay for those minimal prices either because they can't afford anything else, or strictly because it's convenient for them to spend that little so that they have more money left over to do more stuff in their life elsewhere.
But there are also people that are willing to sacrifice and make changes to their lifestyles and spending practices to accommodate the impacts of their actions.
The same is true with corporations. Some large corpos in the world are actively trying to move towards sustainable, circular economies. I'm doing a lot of research right now into the textile industry, and two of the biggest corporations in that space that I've seen are doing decent work on the two fronts I previously mentioned are Lenzing (TENCEL™) and Aquafil (ECONYL®).
Lenzing uses wood of various species from places in Europe, all managed well and FSC/PEFC controlled, to draw out fibers and filaments that are just as fine and useful as polyester fibers/filaments, yet with the added bonus of biodegradability. They also recycle cotton clothing from collection centers in Spain and some larger textile service companies in southern Europe and mix that in with their wood-based feedstock to produce the same rayon fibers.
Aquafil runs on a similar model to Lenzing, except they base theirs on nylon instead of rayon. Aquafil collects ghost nets from around Europe and South America, along with other corporations' scrap nylon (pre-consumer waste) and post-consumer waste from a number of brands (e.g. sunglasses, jackets, etc.) to regenerate nylon back into the same quality as you would find in virgin materials. Now, I don't think that plastic is sufficient anymore thanks to the non-degradable waste associated with it, but it's better than nothing.
Are there flaws with those 2 companies: of course. Their chemical processes might not be 100% closed loop and their claims might be overexaggerated in ways, but it's better than nothing.
Anyways, what this examples shows is that there are corporations and even people on the ground that are willing to make more sustainable choices because they legitimately see the benefit of doing so compared to convention. Someone else might describe this as a form of an adoption life cycle, where you have those more willing to change and those less willing to change as practices and habits shift over time.
Could government help with that? I believe so. I think that's just one lever of change though. If you've been following solar PV growth over the last decade and a half, then you know about the "contagion" phenomenon: some early adopters pick up solar, only for considerers and even late adopters to do the same as word of mouth and other social drivers influence decision making at a people level.
Could the same happen with other sustainable choices in the economy? I fall more into the early adopter camp, so I would say yes. I think corporations spend a lot of time and marketing convincing their customers that said corporations are the best and only options and that no other alternative exists out there: when there absolutely is or might be. Perhaps all it takes is demonstrating to people, doing, not talking, walking the walk, to change their minds. I think the same tactics could be used, in addition to government intervention.
Bottom-up + top-down is the strategy I've heard described by many proponents of sustainability, most notably Al Gore, and I'm all for it too. Luckily humans, at least in some countries around the world, live in free societies and can divide and conquer to work on both of these fronts to affect change.