All of what you're describing sounds like PR to me. The fact of the matter is Starbucks are reducing plastic straws and there is no law telling them to do so.
It's partly PR, and partly the ability to do things on your own terms. You do not want regulations forced on you, that is bad for the bottom line. You need to be in control. This is the story with self-regulation across industries.
> You do not want regulations forced on you, that is bad for the bottom line.
Also, self regulation can be safer in terms of come-back.
Where under an external regulatory pressure a misstep might result in some form of fine or at least a public outing. With self regulation many things can be more easily wrapped up with "oops, butter fingers! sorry, won't happen again" and all that might be more readily kept internal rather that having some form of issue reporting requirement enforced by the regulations.
But it is the companies creating positive PR by getting ahead of expected pressure.
I think what the earlier poster was talking about is using the relationship the other way around: the public using their relationship with the company to say "I could always vote with my feet/money you know, you might want to consider...".
It amounts to the same thing in the end (the pressure they are trying to stay ahead of is created by governments reacting to social change and environmental issues) but the earlier post was talking about more direct action. The more direct route can be quicker, but it requires more effort (well, some effort from more of the public) to be truly effective.