It is tradition in mining, oil and gas, agriculture and environmental fields to determine particle size distributions by sieving alone. This is a legacy from long before the advent of modern techniques such as laser diffraction and x-ray attenuation (Sedigraph) techniques, and the automated control system jiggery-pokery we see the benefit of today.
Many industries still adhere to older sieving standards that they have been using for so long, without realizing that there’s a cheaper, quicker and more accurate way. New standards, such as ISO13320, are in place to validate automated sizing techniques as an alternative to older methods.
As well as the obvious benefits listed above, there are a few other differences between the results obtained by sieving as opposed to laser diffraction or Sedigraph. Sieving analysis gives a mass percent size distribution, which is influenced by particles with hetrogeneous densities. Sieving also measures the second largest diameter, rather than the average, hydrodynamic or aerodynamic diameters. Sieving is insensitive to morphological properties - which may be considered more fully with other techniques.
That doesn’t mean sieving is entirely redundant! Many automated techniques are only suitable for particular size ranges, and sieving is required outside those size ranges to create a complete picture.