Also, the Decepticons' favorite way of collecting energon is to steal it from our own energy stores, which requires us to have infrastructure and population to build more infrastructure.
You don't kill the milk cows when they're still of breeding age, after all.
The art is awesome. However, is not accurate. Bumblebee's chest area should have the VWs cockpit, not the front of the car (which formed the feet in the cartoon and the G1 toy).