Same as with other iconic voices like Donald Duck, Micky Mouse, Scooby do, etc. I don't think there's anything wrong with them wanting Optimus to sound like Cullen. Cullen can't do it forever and it's nice to see younger talent getting a shot at recreating that iconic voice. Tilman did a decent job. I do agree though that something was lacking in the voices. But thats probably more due to the voice directing than the actors..