One of the unique facets of Army leadership is the concept of the leader being responsible for “all the x-element does or fails to do.” It’s an incredible level of responsibility, and it essentially applies to every echelon (i.e.; the Team Leader is responsible for all his team does or fails to do, Company Commander, Battalion Commander, etc.).
The way this usually manifests itself is a leader being called into his boss’ office and being asked: “Why did Private Snuffy get wasted and smash all of the windows of the Generals’ residence this weekend?” The question is typically asked in a manner which suggests you had something to do with it. Likewise, if word gets around that “something bad” happened somewhere in a formation, one of the first questions asked (among officers, anyway) will likely be “Which platoon was it? Which platoon leader?”
Dumb things happen in the Army, and soldiers make mistakes. Good leaders recognize that while it is doctrinally correct that the platoon leader is responsible for everything in the platoon, good or bad, there is also an absolute limit to what he or she can immediately control. If a soldier in a platoon gets a DUI, it is likely that whole chain of command will be standing on the carpet answering for it. Ass chewings will commence, lessons will be learned, and everyone will go on about their way.
Sometimes, while taking said ass chewing, a junior leader (or even a senior leader) can feel frustrated for being blamed for the indiscretion of a subordinate who might have two or three subordinate leaders.
“How the hell was I supposed to stop Specialist Ronald from driving nude through the front gate blasting Ride of the Valkyries!?”
Without question, the reality of the doctrine is such that an individual leader cannot, within reason, fully account for the actual failures or successes of a formation. That is, the platoon leader cannot through sheer will or even the most immaculate planning and execution carry the true responsibility for success or failure. There are too many other leaders and factors involved.
But the reason this high burden remains is because without it, it lets leaders off the hook. If the platoon leader is not responsible for everything his platoon does or fails to do and can simply pass the buck to a subordinate leader for a problem soldier, there is no great incentive to shape the platoon to accomplish goals.
The burden of leadership is absurdly high precisely because the stakes are also high – especially in combat.
Of course, like I indicated earlier, the adage is usually uttered for soldier mishaps and minor discipline infractions. The best platoon leader in history will have a soldier who inevitably does something stupid that will get the platoon leader an ass chewing or nasty email from one of his bosses. If he is wise, he will take it, learn from it, and que sera sera.