Everything we do, we do because somehow it benefits us.
We go to work for the satisfaction (I hope) and because we get paid. We smile at a stranger because it feels good to be nice (and perhaps we'll get a smile in return). We pick up litter when no one is looking because telling ourselves a story about being a good person is worth the effort.
Some people have figured out that charity is an incredible bargain. For the time and money it costs, the benefits exceed what could be attained in almost any other way. A bargain compared to chocolate, or an amusement park visit or buying a shiny new car you probably don't need.
For some, the benefit is in the way society respects the donor. Hence buildings named after Andrew Carnegie or Bill Gates. For many, though, hidden charity is worth far more, because the incentives are purer. A donation earns you peace of mind.
I'm fascinated by people who see no benefit in donating to charity, who, in fact, see a negative. My hunch is that for these people, the worldview is: if charity is important, I better give more. If that's true, the thinking goes, then whatever I give isn't going to make me feel good, it's going to make me feel worse… for not giving enough. Easier to just avoid the issue altogether.
I think marketers of causes that do good have a long way to go in selling the public on the core reason to give… don't give because you get a tote bag, or a prize at the charity auction or even a plaque. The scalable unique selling proposition is that being part of the community is worth more than it costs.