One of the most important codes of honor when it comes to the military, especially the United States Marines, is "no man left behind". This also includes the body of someone killed in action, and is taken most seriously by the Marines. However when a special operations unit like Marine Force Recon is on a black ops mission they know that in the event of capture the government might be forced to disavow them for the sake of national security and the greater good, and also because they don't want to risk the lives of their fellow operatives in order to retrieve their body. This is one of the reasons why black ops missions are volunteer only, someone can't be ordered or forced to go on such as mission. This is also something Major MacKenzie should be well aware of, yet she acts as if she is ignorant of this fact.