In Ancient Greece, hospitality meant a lot more than giving your guest the most crumb-free seat on the Ikea couch. They had a whole word for the relationship between guest and host: xenia. Zeus was in charge of this relationship, and it was one of the ground rules of ancient society. Guests bring news and stories from the outside world; hosts provide food, shelter, and even money if need. And both sides give whatever gifts they can. Why would anyone treat a total stranger like that? You're paying it forward: someday, you just might need someone to do the same.
Because they violated the laws of hospitality, both Polyphemos and the suitors got what they deserved.
The Phaiakians' remarkable hospitality towards Odysseus was ultimately not worth all the trouble it caused.