Why do items require units?

Items require units for two primary reasons. First, units are needed to fully describe item quantities. For example, it is not enough to say, "We have 25 sodas in stock." You would expect instead to hear, "We have 25 cases of soda in stock." Second, units make it possible for the system to convert items from one unit to another. If you stock items in one unit and sell them in a different unit, then the conversion is only possible if units are assigned in the first place.