While there are certainly good reasons to maintain emotional distance between the people giving orders and the people going out and getting shot at, I strongly suspect that social separation does more of the work there than formal grade separation. The latter can be a means of enforcing the former, but there are other possibilities as well.

Western-style air forces or naval aviation are probably the best example: all the people doing the shooting are officers, but they're getting orders from a significantly higher echelon of officers (who, in the Navy, might not even be on the same promotion track). Even in armies, though, there are significant jumps in danger and responsibility between company-grade officers and field-grade, or between field-grade and general officers.