I don't think a ship this size has the space for a political officer and their henchmen.
Which I suspect would be another bonus for a Naval officer keen on command. And would likely make many officers promoted from Raider commands unconventional - at least by Imperial standards. Some officers might even prefer command of a Raider or maybe even Raider squadron command to commanding a Star Destroyer for precisely that reason. Such unconventional officers might be unpopular with certain members of Imperial high command, but if they're successful, that's all that matters. Command of Raider s and similar small capital ships might even make for a whole cult within Imperial command consisting of former Raider officers. If Admiral Thrawn is going to make it into canon, I suspect he would be the patron saint of Raider officers - and possibly a former Raider (or other corvette) commander, himself.
A fair point; I just finished reading Aftermath, which prominently features a former Imperial loyalty officer. Perhaps that's why it was on my mind.
All the same, the Empire has a habit of concentrating the best & brightest officers and crew in the largest, most impressive postings. The Death Star(s) had all of the best crews. Next would be Super Star Destroyers, followed by the newest Star Destroyers and so on. Raider crews, as with any of the smaller ships, could certainly be turned into quality "sailors" through experience & good leadership but I suspect that it would lead to a new posting on a bigger, better ship.
As an aside, I've seen other material that indicated that indicated that stormtroopers made up only a relatively small portion of the Imperial military, but it's all now of questionable veracity. We may never know the answer now that "canon" has shifted so much.