It is considered as a common-sense for a visitor to once decline an offer of bubu zuke, and, therefore, if he accepts the offer and takes it without reserve, he will give an impression to the host that 'he or she is bold.'
ぶぶ漬けを勧められても一旦はこれを断るのは常識であり、もし遠慮も無く真に受けて食べてしまうと、家人に｢あの人は厚かましい｣という印象を抱かれてしまいかねない。