To me, I've always thought that when the guests gives money to the hosts of the party is a gesture of helping the family out with the costs of the party. Whenever I have a party at my house, a lot of my parent's friends would come over to help with the cooking or bring something to the party. Those who don't just give money, but that doesn't mean those who came to help doesn't give money too. I dunno about some people, but I've always felt that when our guests comes to our party and gives us an envelope with money inside, helping out, or just bring's food that those people are very thoughtful. Besides, they're all like relatives and not just some people we know.