When I was younger I was taught to do courtesy calls for every meals, but only whenever someone other than immediate family members were around. Say I'm halfway through my dinner and my uncle and auntie dropped by, I'd go "uncle, auntie, have you eaten yet?" or "uncle, auntie, are your bellies full?" and they'd acknowledge by saying "yes", "okay", "hmm" or just a nod. It might make no sense to some people, but the purpose of this courtesy call is not asking them to share your food, but to dispel the negative connotation of "quietly eating food behind other people" aka its the willlingness of wanting to share the food, not sharing the food itself that's important.