Why is the 16th Karmapa visualized rather than the 17th Karmapa in Karma Kagyu?

From what I have seen observing Kagyu ceremonies, the 17th Karmapa (either of them, actually) is treated with great awe, respect and reverence. However in their daily rituals, Kagyu buddhists usually visualize the late 16th Karmapa. I assume this is the result of a certain prescription within Karma Kagyu but I was unable to find explanations of this on the Internet. So, why do Kagyu followers visualize the late instead of the current holders of the Karmapa office? Does this have to do with the status of the late living Buddha as opposed to the living living Buddha?