If I consume 50% less dairy products, for instance, it will cause a noticeable negative impact on my life.
The impact it will have on the environment will not be at all noticeable. (and it wouldn't be noticeable if it were multiplied by tens of thousands)
It isn't realistic to expect change by relying on consumers to negatively impact themselves for some unmeasurable positive.
On the other hand, it is not at all unrealistic to have those same consumers vote for regulation. The amount it increases the cost of dairy products would likely be outweighed by the positive impact on the environment. It works because the impact of action on themselves, both negative and positive, are divided up by all the people.