That conclusion doesn’t necessarily have to be as pessimistic as you seem to imply (“we do what is most convenient to us”). An alternative hypothesis is that people to some extent do want to do the right thing, and are willing to make sacrifices for it—but not large sacrifices. So when the bar is lowered, we tend to act more on those altruistic preferences. Cf. this recent paper:
[Subjective well-being] mediates the relationship between two objective measures of well-being (wealth and health) and altruism...results indicate that altruism increases when resources and cultural values provide objective and subjective means for pursuing personally meaningful goals.