I've seen it run both ways, with GMs sometimes taking on hosting duties ("Thank you so much for coming to my home! Have some pulled pork.") and other times expecting snacks to be heaped upon their GM throne ("If you're going to come to my house, you're going to contribute to the snack fund.") Those are two very different attitudes, and it can lead to etiquette confusion when you move between groups.
My question to the board: How does your group play it? And more importantly, how do you convey that information to the rest of the group? Do you make a formal point of it in Session Zero, or just assume that everyone will pick up on subtext?
Comic related.