No one cares about you

…unless it's in their best interest to do so.  de Tocqueville put it well:

"an enlightened regard for themselves constantly prompts them to assist each other" – Alexis de Tocqueville, Democracy in America

It's generally a waste of time to try to get people to support you or your cause on their own.  But it may be extremely beneficial to help people understand how supporting what you are trying to do will benefit them.  The purely short-sided greedy people won't get it.  But the more enlightened will see the longer term payoff.