Who do you think are military contractors? Most of them former military and they are out of military and into contractors because it pays more and there are also different standard on discipline. Also military would never take a man with a criminal record which is not an issue for a private contractor.
Your prior post indicated the Russian contractors were prior Russian military who had behavior and conduct issues while in the Russian military. I pointed out that is illogical and possibly irrational.
Besides the fact those types are the least likely to return to military employment it is standard contracting procedure to require discharge papers and service records when applying for such work. The contracting company has no requirement to employ them and will not accept the bad conduct types.