Personal enrichment is an all-too-common reason for graft. Enron, DeLay, investment bankers.

"Everybody does it" won't fly in the Hessian company. They don't do it. Except the handful who do and are kicked out. The point is to set up one of the main differences between the Hessians and the Martians. One is generally honest and law-abiding (even as they enforce the laws: cops aren't above the law, after all); the other ignores graft and corruption unless it really screws things up (ie, undermines the leadership's authority, etc).