Chosen answer:There is no reason to think they can't. They simply choose not to. They may feel it's too deceitful.
Actually in this movie (when joining up with bumblebee and the others after they pick up the All Spark) and Revenge of the Fallen, Ironhide uses holographic humans in his cargo bed. Also, Arcee and the twins use holographic drivers at the beginning scene in Revenge of the Fallen.
Chosen answer: There is no reason to think they can't. They simply choose not to. They may feel it's too deceitful.
Actually in this movie (when joining up with bumblebee and the others after they pick up the All Spark) and Revenge of the Fallen, Ironhide uses holographic humans in his cargo bed. Also, Arcee and the twins use holographic drivers at the beginning scene in Revenge of the Fallen.