Visible crew/equipment: When Sam is at Bobby Bolivia's cars dealership intending to buy the Chevrolet Camaro and all the cars' windows explode, as the camera turns around a shocked Bobby Bolivia the shadow of a boom microphone is visible on his face.
Visible crew/equipment: When Sam is brought by his father to the Porsche's dealership at the beginning of the movie you can see the camera car reflected on the building's glass while chasing them.
Visible crew/equipment: When Sam is talking to Barricade, in the shot taken inside the car, a camera is reflected by the windshield. (00:49:55)
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.