Why are the walls of the flask washed with de-ionised water during titration?

The walls of the flask are washed with de-ionised water during titration to ensure that all of the titrant is combined with the analyte and to prevent any loss of reactants. This helps maintain the accuracy of the titration by ensuring that the volume of the solution being titrated is not underestimated. Washing the walls also minimizes the risk of contamination and ensures that the measurements reflect only the intended chemical reaction.