In the original story, the war had been going for so long and they were so drained of energy that many of them couldn't use their powers anymore. Knowing Ironhide, his armor power was probably permanently disabled from battle. Guys like Prowl and Jazz, otherwise skilled combatants, had to resort to firearms. They probably decided long ago that was the most efficient use of energy. But a few of them have managed to keep theirs. It wouldn't surprise me if they purposely kept Mirage in top priority condition because his power is so useful. Others like Brawn and Cliffjumper kick in internally, so it's not as taxing. Trailbreaker is an interesting case because his power, one would think, uses a massive amount of energy. Thoughts?