It seems like every culture expects guests to want to eat regardless of their circumstances, and if you refuse, you’re automatically rude and insulting.
If I offer you food and you refuse, I’m going to be quite happy. It means I get to save money and have more food to myself. I ain’t offering a second time if you say no the first time :maduro-coffee:
The system developed during times of famine. The first offer was to show that the host wanted to share food with the guest, even if they didn't have any. The first response must be a refusal so the guest allows the host to save face. The second offer is the real offer, and you can accept or reject that one because it is an actual offer of food, not a forced offer.