We helped the dog despite a variety of risks to ourselves, despite not knowing when it would end, and despite being in a hurry. We didn't do it with any expectation of reward or kudos. And although we do train and board dogs as a side gig, we're already booked enough to be choosy about clients, so we weren't doing it for potential business.
We did it because ignoring the dog felt bad and helping the dog felt good. That is, it was completely selfish on our part, but we still did the right thing.
But at least a dozen other people just walked by the dog as if they didn't see it. It was off leash, unkempt, and clearly scared. They saw it, but they just walked on past. Why? Because, for whatever reason, they didn't feel badly enough or wouldn't feel good enough if they helped.
I don't litter, either. And I take some personal responsibility for the litter of others. Again, because it feels good (or, in this case, living in a marginally cleaner city feels good). It also feels good knowing I might not be the only one who does so.
Neither of these makes me a good person. There's one instance where I know I don't do the right thing: I don't visit people in hospitals unless someone else drags me along. The experience, for reasons I'd probably need a psychologist to figure out, is painful for me, and whatever reward I get visiting the person is dwarfed by that pain. Even the shame and embarrassment of being a person who doesn't visit people when they're in the hospital isn't enough of an incentive to go. I need an external incentive. I need a friend to say, "Hey, let's go visit Phil in the hospital" or I'll be 'too busy' to go.
We all 'think differently' than each other. We're all doing what feels best. We all have different internal incentives and disincentives. So, for any sufficiently large group and any desired behavior, external incentives are required to get some of the people to exhibit that desired behavior.