Neil is the Butters (South Park) or Brett (Archer) of the Brotherhood. Everything bad happens to him and he dies the episode after he's introduced. But his death affects the mental state of Nora, Jamison, Sierra, Cornelius, and Oliver as the Brotherhood have to be an elite fighting force and Neil was actually a good fighter and to have gone down not even a few days after being deployed makes them doubt how powerful they are in an unpredictable wasteland.