Probably what happens when the director follows the script and tells a story that makes sense.
I still think that they aren't showing enough Decepticons in the commercials, even if they probably don't have much screen time, it will make the movie look more like a robot action movie, rather than a human-robot drama. People aren't expecting Bay-explosions, but we don't want to put off too many of those millions of past Transformers movie goers hoping to see bot-v-bot action who might think it is just about a single robot exploring earth and human interaction, with a small bit about the military wanting to capture him.