It's the fault of the Treasury. Too many cutbacks. If they had left a regiment or two spare, then those units blessed with the Royal presence could simply have been sent somewhere non-dangerous.
This is also down to the government's desire to avoid the slightest chance of the very bad news that any unfortunate incident involving this particular officer would generate. I am sure that HM believes he should do his bit, the rest of them as well - after all, he is the "spare" (and ginger at that). However, the spinners in Whitehall must have twitching sphincters at the thought of something happening to Hazza and the media disaster that would follow.