Thrust, a "melee Decepticon lieutenant", is in charge of the lighter long-range Decepticons. Which works out great for him, because it means he can send them out on the dangerous missions. This way he doesn't have to get up close and personal with the Autobots himself.
Thrust is a colossal coward; he's as "brave" as they come when it comes to terrorizing unarmed humans, but once even a decently-armed human force comes into play, let alone fully-armed Autobots, Thrust is off like a shot. He has no intention of hanging around and getting killed.