Firstly, because the fire is in the bit that can get a bit hotter than the rest. It is also well contained. Secondly, you are on the ground and you have time to get the appropriate checklist. Thirdly, although spectacular, there is no imminent danger to the aircraft. Lastly, do you really need another memory item? The difficult bit is to convince the ground crew and passengers that this fire is not an "Engine Fire".