Why must the glassware be dry before beginning and experiment?

Some experiments use chemicals and water, glassware for such experiments must not be dried. But glassware for the experiments that has no water in them must be drived, so water do not get in the reaction. E.g. in Grignard reactions, if water gets in a reaction, alkane will be produce instead of an alcohol. You will get not what you wanted.

But if you will perform Acid-Base Reactions, in the end you will get water anyway, so extra water that was in the glassware will not change anything.