[PeterPrinciple]

According to a few other articles there may be more to be earned entrepreneurally or in the black market.

Could this be a reason and if so then they may be losing the cream and the rest are staying?

[KellyAdmirer]

I understand your point. I think anyone leaving over salary or perks or whatever is by definition just a mercenary, though, so they may be the "cream" in some terms, but not the "cream" in terms of who I would want manning the machine gun next to me.