Henckles does drop forge their blades. It saves a MAJOR amount of steel from becoming grinding dust. Big expense savings.
I have forged some satinless. I still do forged CMP3V, mainly because of the novelty, and that few others will. The problem with forging stainless steels is that most are air hardening, and do not move easily under the hammer. They are "red-hard". If you allow the temperature to get high enough to austenitize the steel ( the temp where the ally elements are in solution and will form martensite when cooled rapidly enough), it will try to harden once it cools, and if forging is performed when this happens, the steel usually crumbles, or at least cracks. So the steel needs to be kept above the austenitizing temp ( high enough to give a window of time to forge before it begins to harden), or below it so it won't air harden to the dergee that it will crack. So, it becomes more trouble than it is worth since little if any performace benefit is obtained. If the forging isn't done properly, it is detrimental to the steel.
Forging produces a lot of stress in teh steel as well. To remove forging stress, most steels are normalized and annealed. Annealing stainless steels takes several hours and the temperature must be closely monitored to do a proper job. Most forgers don't have a digital furnace, so again, it becomes more trouble than it is worth.
I have forged ATS-34 and 440c, and it just isn't worth the time to me. I would rather do stock removal with S30V if a custoemr wants stainless steel.