Why do companies have responsibilities to shareholders?

This is, naturally, a huge question about which many books have been written and countless ideological battles been fought, but I still cannot grasp the issue.

As I understand it, the premise is as such: shareholders provide a company capital in return for certain rights (usually voting), so the company assumes a moral obligation to look out for the best interest of the shareholders above all else. To please shareholders, companies pursue steadily increasing quarterly returns and dividend payments.  I understand that a company wants to please shareholders so it does not incite a revolt (throw out the boardroom), but the coordination costs for millions of shareholders is so high that this hardly ever happens.  (What happens instead is that a couple really powerful shareholders emerge and the other shareholders are along for the ride.)  But if a company accepts this minimum responsibility, it will probably also be acting in its best interesting: investing in long-term R&D, producing a quality product, ensuring its employees have a decent standard of living, etc.

But instead companies assume that their sole responsibility is to their shareholders.  Seen this way, GM is no longer a company which makes cars; it is a way to redirect income from the buyers of its products to its shareholders.  Microsoft no longer sells software; it redirects income from the buyers of its software to shareholders.  In other words, companies which make core competency shareholder returns lose their focus on producing estimable goods.  In a sense, they lose sight of their greater role in public life.

Instead, I see shares as the right to gamble.  If I buy GE at $9, I am hoping I can find someone later on who will buy it from me at more than $9.  If I am buying it for its strong dividend, I am essentially saying: “GE should pay me $1.24 per year per share instead of investing in R&D, improving its manufacturing, or hiring better managers.  My short term profit is greater than the long-term benefits of reinvesting their income.”  Instead, I should buy stock because I like GE, GE makes good products, GE will make better products, and so people will pay me more later for the share than I spent on it.  And GE especially does not owe me anything when I buy a share from someone else because that money went to the previous shareholder and not the company.  Why should GE owe me something when I did not give them anything?  It’s like not paying your taxes and then expecting to get social security benefits.

I understand that stocks are beneficial for companies because they can reap equity infusions, but those infusions are so rare that I do not see why they merit the grovelling to stockholders that has wracked our country for the past thirty years.  If we had paid more attention to the health of our companies and not the strength of our dividends or the size of our margins, I think a lot of our current problems would not be as big.  So can someone please explain to me what I’m missing?