This holds even more true with matters that will cost the company a lot of money while giving no added value to the shareholders, such as those externalized costs by polluting the environment.
Why would any Apple shareholder willingly take a hit to their portfolio just for a "nice feeling in the tummy about having done the right thing"? Not to mention that with most publicly traded companies there's only one "right thing": Increase shareholder value, everything is optimized around that and pretty much only that.
And sure you can vote people into Congress, but what leverage do you have that those people actually stick to their word once they are there? Imho that's one of the major flaws with most representative democracies: There's only positive voting, you can't "vote out" people who didn't hold up their end, you can only try to replace them with somebody who got more votes and hope he/she keeps their word.
In the end, this is also a question of how do we want our economies to be built: For supposedly perpetual gains and growth or for a sustainability which accounts for the actual scarcity of resources not easily measured and accounted for, like a clean environment.
As far as owning Apple, unless you are a major (read: majority) holder, good luck trying to make any difference because the actual majority holders want the profits, and they are not (as much) concerned about the externalities involved.
Actually they do, if enough of them care loudly enough to organize and push back. Constituent participation in the ACA Repeal debate earlier this year caused the measure to fail. They had to sneak a small, partial repeal into the huge tax bill they just passed. When the dust settles, blowback from that sneak might cost more then a few their jobs.
In practice this basically rounds to zero on most issues, especially over time.
Otherwise, what's the point of Congress if we aren't going to leave it to them to figure things out?
That's the point of my pessimism – modifying your own behaviour does not make any difference. Even if millions of people boycotted iPhones that would still be a smaller loss for Apple than changing how they're doing things, because doing things right is suicidally expensive when most of your customers don't care. An even smaller loss would be doing some marketing to make most of boycotters ambivalent enough to forget the whole thing.
Using Apple just as an example, could be any company or government.
There's a difference between "me" and "we". "We", the majority, could, if we cared. "I", alone or even in a sizeable minority group, can't make a difference, regardless of how much I care.
People can certainly be very self centered, but a big part of this _collective_ culture of either caring or not caring for various things has been manufactured entirely artificially by governments and corporations alike.