"Techniques for vegetative propagation include:

• Air or ground layering.
• Division.
• Grafting and bud grafting, widely used in fruit tree propagation.
• Micropropagation.
• Stolons or runners.
• Storage organs such as bulbs, corms, tubers and rhizomes.
• Striking or cuttings.
• Twin-scaling." --Wikipedia

Nothing wrong with division as long as it works. It's not done as much in the commercial realm just because it's more labor-intensive for the number of plants produced -- compared to cuttings, seeds, etc. However divisions may be the only practical way for the home grower to propagate some plants -- I'm thinking, for example, of Cattleya orchids, Hosta varieties, some hybrid Hellebores, etc. etc.

A good horticulturalist knows which propagation methods work best for which plants.