In order to help prevent a large epidemic, those in charge of marketing the idea of flu vaccination (an extremely useful tool) rightly appealed to our naturally selfish nature:
"You need the flu shot" "Protect yourself from the flu".
I think they wanted to use the fact that most people have an innate self-preservation instinct, and they wanted to use that fact to achieve the goal of maximal vaccination, in order to prevent another pandemic (an honorable goal indeed).
(As much as we might proclaim otherwise, most of us really don't care a whole lot about a bunch of anonymous people, and certainly not about a population of say, a couple hundred million people -- so a more honest marketing tactic would never have worked.)
So it is true, the flu vaccine may indeed help YOU; but look up Herd Immunity. We do it as a group in order to maximize the immunity of the community as a whole to help prevent (or minimize) a huge problem - that pesky old "1918-1920, 75,000,000 dead people thingy".
In short, if people were told, "do it for others" that marketing scheme would've fallen flat on its face.
Unfortunately, these days, we have a growing pool of people who believe themselves to be smarter than epidemiologists, doctors, and science in general - or they are skeptical (which is perhaps a more refined state of 'thinking they are smarter') and refuse to become a part of it.
(In addition, I think there is also a huge lack of 'team' or unity in our country, and our world.)
Finally, I know many of us will gladly do incredible acts of charity for our fellow man. However, I don't think many of us can see that we can easily do one of the most charitable acts possible by being vaccinated; and preventing someone else's death.
It is truly an interesting study in human behavior.