Why is it important not to have fingerprints on the cuvette?

Its important not to have fingerprints on the cuvette when using a spectrometer because by using a spectrometer one measures the amount the amount of light that the solution in the cuvette absorbs at a certain wavelength. This tells you how much of the solute is dissolved in the solution. So if you get fingerprints on the cuvette, this could interfere with the light absorption and cause your readings to be incorrect.