Being a soldier is about effectiveness in combat. A street thug can intimidate too, but he'll make a rubbish soldier. The praetorians of the Empire were simply glorified bodyguards and meddlers compared to the real soldiers, no idea why some people are making this bizarre reference to a unit that existed before the Empire did under Octavian. That has nothing to do with the praetorians as they existed in Imperial Rome, as basically a kind of city watch; often corrupt, and with very limited battle experience for the most part (compared to the real armies anyway). It was the real armies who determined the emperor in times of Civil War, no matter how the praetorians tried to get involved in it.