A man who calls his kinsmen to a feast does not do so to save them from starving. They all have food in their own homes. When we gather together in the moonlit village ground it is not because of the moon. Every man can see it in his own compound. We come together because it is good for kinsmen to do so.

Notice how the speech is built. It never argues for togetherness. It removes every other explanation until only togetherness is left standing.

Why call your kinsmen to a feast? Not to feed them — they have food in their own homes. Why meet on the village ground when the moon is full? Not for the moon — every man can see the moon from his own compound.

So the feast is not really about food, and the meeting is not really about the moon. Both are occasions. The reason is the one the speaker saves for last and says plainly: it is good for kinsmen to be together.

What makes it worth reading twice is that he offers no reason beyond that. We tend to justify time with our own people by calling it something useful — an occasion, a duty, a chance to talk business. Achebe's speaker refuses to.