This article is from the Food Preserving FAQ, by Eric Decker email@example.com with numerous contributions by others.
For a couple of reasons. One is safety. When meat is cold smoked
its temperature often stays in the danger zone for several hours or
days. Many environmental factors of this treatment are such that
the growth of dangerous bacteria is greatly accelerated. The
curing of the meat inhibits this growth.
The other reason is traditional preparation. There are many curing
techniques that were developed in the days before refrigeration
that are continued today for traditional reasons. A good example is
Old time butcher shops closed every weekend. Ice, the
only refrigerant available, could not dependably hold
fresh meat for two days. To keep unsold meat from
going to waste, the butcher soaked the meat in a strong
brine or covered it with coarse salt to trigger osmosis.
The grains of salt were called "corn" in England, and the
name "corned beef" stuck with the product.