What is the real reason that the Doberman is not used as a police or military dog in the U.S. anymore?

Now I say the U.S. because I honestly don't know if they are still used in other countries. I have heard many different reasons, such as they can't handle extreme weather, another is they are more expensive and harder to train then German Shepherds are. Now these two reasons are brought up a lot and easy to understand but then there are other reasons that contradict each other (i guess that's a way to put it), but some reasons that are given is that the doberman in America have had pretty much all aggression and the nature of what they were originally bred for bred out of them and then you have the other side that say they aren't used because they are to unreliable and when they get trained to do the job they get to aggressive and the handlers can't even keep them under control or they are to unreliable in the since that they can't get them to do the job and if (for lack of a better term) when poop hits the fan the dog will not do its job but instead run the other way. Now I ask this because I was working with the kennel master on my base the other day and I asked him this same question and he like others had many different reasons, so my question is, What is the actual reason?