I was recently in a New Orleans hotel bar and for several days stared at the open bottles of wine stored in their cooler. There was an odd assortment of red, white and rose wines. For kicks I kept a mental note about their levels. There was about a glass of wine left in two opened bottles of rose. In four days, the level was the same.
With this much oxygen left in the bottle over this period of time, the wine has suffered dramatically. Anyone who gets a glass of it will be disappointed and probably assume the quality was a result of poor wine-making. Obviously, it is the result of poor wine preservation.
Good bars will throw out left over wines at the end of a night just to assure customers that they are getting fresh wines. However, there are far too many restaurants and bars who wouldn’t think of throwing away any wine. Witnessing this is the very reason I always ask how long a bottle has been open before ordering a glass of wine. You should too.