Because it costs money to just replace a part that may not be bad. They check the part and then they tune the computer to tell if the part is failing and causing to much vacuum that will hurt things. It is cheaper to reprogram than to replace a part in every single Ford Focus. This is the same as any recall. Check then replace if needed. Mine is fine for now so I am not concerned with the recall. And all recalls on voluntary on the consumer side. You do not have to get the recall done and no one will force you to or punish you for not doing it. If the part fails or causes damage it will still be covered under the recall if you chose not to actually do it.How hard is this part to replace? If it's easy, why not just replace it?