Consumer choices can influence industries, but it is impractical to solely rely on this to drive ecological change due to factors such as lack of awareness, inconvenience, habits, price and limited to no alternatives. Government subsidies for ecologically detrimental industries and the lack of subsidies for ecologically beneficial industries worsen the effect. Improved legislation is necessary to address these issues by enforcing ecologically beneficial industry practises and guide consumers.

Verbose:

I agree with you partly. Yes, consumer choices do affect which companies get money and which don't. But I would say that consumers are not completely responsible for the practises of a company. If a company chooses to power their production based on fossil energy carriers there's not much a consumer can do about it. Sure, they can stop buying from them. But for that a lot of things must happen. First of all they must know about it. And if it's not printed fat on the packaging or news are screaming about it, there is a high probability that they will never know about it. They could ask the companies themselves. And even if companies would be transparent and honest about their response, there's only a small fraction of people who would do this. That's because it's inconvenient. As ugly as it sounds, people hate inconveniences. A lot of people don't want to spend their precious free time with writing or calling the hundreds of companies, whose products they use, to ask about their production practises. Finally, if consumers eventually learn about the ecological impact of their products, they still need to collect a significant amount of mental energy in order to make the conscious decision of not buying them and possibly looking out for alternatives. That's difficult, because people easily get used to stuff and it's psychologically hard to change habits. And they'd need to do this for every single product they use. Even worse, in a critical amount of cases there aren't even alternatives available to consumers. If you continue buying the wrong products (in an eco sense), because you don't have access to an (affordable) alternative, that will send the wrong signals. The market won't see an increased demand for ecologically friendly products in these (significant amount of) cases, but quite the contrary. I don't say that it's impossible, clearly humans seem to have the capacity of intelligence and can be educated to do better, but I claim it's impractical for the everyday life of the masses. Especially, we don't have the time to wait until the majority of people is able to change their consumption behaviour. That's why we need laws, such that law makers do the hard work of paving the way for ecologically beneficial industry practises, so the Jon or Jane Doe going to the grocery store after a long day of work doesn't have to worry about which products to buy.

Besides, in a lot of countries fossil based energy carriers are still cheaper than environmemtally friendy alternatives, sadly. If companies start to completely switch to green energy, this would increase the price. Increasing the price can lead to less consumers buying the products. Either because they can't afford it or because they want or need to save money. This again would turn the circle of environmental destruction once more, since the cheaper alternatives, which consumers are looking out for, are usually less beneficial or even detrimental to the environment.

Also let's not forget that also a lot of countries subsidise industries which are major contributors to greenhouse gases, e.g., the meat industry. Meanwhile there is a lack of sufficient subsidies for ecologically better industry segments. I live in a world where an organically grown cucumber is much more expensive than a pack of meat. That can't be right.

We need good laws and can't rely on the behaviour of consumers alone. There's no way around it.