First, it is a more economical product than a traditional litter (or non clumping litter); it will last longer (several weeks rather than just one) and you only have to add small quantities when needed. Second, a premium quality clumping litter is less dusty; it is then ideal if you or/and your cat are dust-sensitive.
Traditional litters are usually more commodities than luxury. They are often inexpensive when purchasing but you have to change it completely every week, clean the box and fill with new litter. And they are also usually more dusty. You only have to remove faeces on a daily basis, since urine is being absorbed by the clay grains. It is an excellent choice if you have to leave your cat alone for several days or have very little time to clean the litter box.