Those in Hommund who are convicted of magic use in Hommund are faced with a choice: execution or enlistment. It is no wonder their ranks swelled so quickly.The Battle Mage Corps is the only force authorized in the use of magic within the range of Rohan's empire. Where they walk the streets in blue coats and shining helms, the townsfolk usher their children inside and watch the passing breathlessly.
Some wonder why the Mages are not more heavily armored. Surely they could be better protected, they could be even more untouchable.
There are two answers to this question.
The first is the reason of practicality. In the interest of breeding an army overnight, it was not practical in the early days of the empire to commission fitted suits of armor for thousands of men. Magic-users, too, are accustomed to long hours of study. While the Mages are trained in competent swordsmanship, both for self-defense and fitness, many more hours are spent studying tomes and memorizing spells. With a light uniform, the fit Mages are free to march for hours and still have a calm, even pulse and a clear head to recall every word of incantation.
To suit up in plate is to acknowledge a change in environment between the tower and the streets. This is going to war. But magic is above all a mind game, and it is important that the Battle Mages be untouched by any stress of a battleground environment, where the mind dulls and slows and becomes subject to urgent gut responses. No, the Battle Mages study in their uniform, in something manageable for constant wear, and they learn to associate it with the comfort of the school, and they will have it like a blanket of safety out on the street.
Likewise with the pervasive use of the uniform. Every Battle Mage must wear it, and so breed the feeling of brotherhood that comes with the identical appearance and close association. So you can see that the Mage's uniform is designed to encourage a feeling of calm, safety, and brotherhood in the face of danger, so that it does not in fact appear to the Mage as danger, and his mind is left unfettered to manage his spells with removed efficiency.
Just as the garb inculcates a feeling of unity between the Mages, the heavy beaked helm forms a separation between the Mage and his surroundings. Inside the helm, outside sounds are dulled, everything is clearly outside the self, and one's identity is definitively anonymous. Those familiar with the psychological effects of masks will see where this is headed. A Mage who cannot be identified by others cannot be held accountable for his cruelty, and uniformity of the Corps encourages the mentality of us-and-them, as does the training of the Mages. They have a power all but their brothers lack, they are superior, they study and are smarter, they are above the peasants and commoners, they are special. They are told this day after day until the townsfolk seem but insects. The thick helm blocks out distracting sounds and the pleas of commoners, anything that might distract from the magical cants that resound in the metal case.
The second answer is more terrifying, and is all that the city-goers know: the Battle Mages do not wear armor because they do not need it. They are nightmares, they are wizards with charms and curses in their defense. There is no use in striking them, there is no use in fighting back.
The best one can do is to stay out of their way.