I have no problem ordering a bottle of wine for just my wife and myself. I do not always drink wine with dinner and therefore the sharing thing does not work as well. In addition I do not know my tablemates preferences and habits and as such do not want to pressure anyone into a sharing situation they do not want to be in. (any more than I want to be pressured into an escalating round of sharing). Buying for ourselves on the first night establishes that everyone else is free to buy without needing to include us. I have had situations where once we were into the cruise a bit I felt more secure in ordering wine for the table but I do not expect that it be reciprocated. If it is great, if not, I will go back to ordering for my wife and I again.