[Bearman]

Originally Posted by xtremerus

Old Chinese custom.
The host may be feel bad that he has not provided enough food, if everything is cleaned up, and you may belittle him.
He may be very poor, and provides the best he can for his guest.
The Chinese leave a small portion on the plate as a sign that he provided enough for the hosts means, and that he has had his fill, and honour his hospitality.

Even if he is still hungry

Well there you go!! Learn something every day. Thanks for that.