The old argument is that it is less costly to dry lumber, if you let nature take you part of the way toward the final moisture content. From a narrow view of energy consumption and capital cost this is of course true, since this method requires less kiln capacity (less capital investment) and shorter drying schedules (drying from air dried to 8% is faster than drying from fresh sawn). However, this narrow focus on the cost of drying lumber is exactly that: "narrow".
Other factors can make it profitable, if not necessary, to control the drying process from fresh sawn. These factors include:
-- Less degrade.
-- Better color (little or no weather stain).
-- No mold and stain problems (provided your kilns are well designed).
-- No capital cost invested in a large pre-kiln inventory.
-- And more minor factors.
The above factors have become increasingly important as lumber resources become more expensive and harder to get. In addition, the better drying quality and often the better (brighter) color can bring you more satisfied customers.