These commonplace acts of generosity - - where no future return is likely - - have long posed a scientific puzzle to evolutionary biologists and economists. In acting generously, the donor incurs a cost to benefit someone else. But choosing to incur a cost with no prospect of a compensating benefit is seen as maladaptive by biologists and irrational by economists.
Comment: Maladaptive and irrational only from a point of view of those who've been ponerized, and thus unable to make the distinction between healthy and pathological thought processes and logic. True human kindness and generosity doesn't require a reason or an incentive.
If traditional theories in these fields are true, such behaviors should have been weeded out long ago by evolution or by self-interest. According to these theories, human nature is fundamentally self-serving, with any "excess" generosity the result of social pressure or cultural conformity.
Comment: To learn more on the sacred rite of hospitality and how it's both the host and the guest responsibility to respect it in order to establish close and cooperative relationship, read Cassiopaea forum's thread The Odyssey - question for all!