Safety valve theory applies where most Imperial recruits are involved. Statistically, based on the world generation system, the "typical" Imperial was raised on a pop 9-A world ruled by a dictator, oligarchy, or impersonal bureaucracy. 82% were raised under TL7 or higher (no firearms), with almost 2/3 raised under TL 9 (no weapons outside one's home, and Big Brother is watching you).
All of which means the typical Imperial military recruit (and likely many a colonist settling the smaller worlds) is someone from a crowded, despotic, high-law world who saw a life of danger on strange worlds under Imperial military discipline as preferable to whatever future awaited him at home. This is more likely to be some itchy-footed wretch with no prospects and little to hold him to his homeworld, or possibly with trouble in his future, rather than someone of more comfortable circumstances and prospects, especially when you're talking enlisted-level.