The ancient Greeks obviously had a very different culture and worldview from us today. A key part of their cultural practice was hospitality, which is still a central aspect of many different cultures around the world. For the Greeks, it was impossible to determine whether the beggar knocking at your door was actually just a beggar or whether it was a god or goddess who would judge you based on your hospitality, or lack of it. In The Odyssey, again and again the value of hospitality is stressed through the many times in which Odysseus himself receives hospitality, but also the failure of the suitors to provide hospitality for guests and the efforts of Telemachus to make up for this mistake. Note how he does this when he greets the goddess Athena, when she is disguised as Mentes:
With such thoughts, sitting amongst the suitors, he saw Athene and went straight to the forecourt, the heart within him scandalized that a guest should still be standing at the doors. He stood beside her and took her by the right hand, and relieved her of the bronze spear, and spoke to her and addressed her in winged words: 'Welcome, stranger. You shall be entertained as a guest among us. Afterward, when you have tasted diner, you shall tell us what your need is.'
Telemachus in this quote demonstrates the importance of hospitality and also brings honour to his household by greeting a stranger and offering them entertainment and food. In an uncertain world where firstly you did not know the real identity of the person knocking at your door and secondly it was impossible to know when you would yourself require hospitality from strangers, it was a key cultural value to always offer hospitality to travellers and those less fortunate than yourself.