First because that's what ISIS leadership wants, is for us to invade. Yeah I know we can make them understand you should be careful for what you wish. But that leads into my second reason, which is I haven't seen anything since Vietnam that leads me to believe we have the political will to fight a ground war till it's ideal outcome is achieved. Whatever form our response, the end goal should be to leave ISIS as nothing but a bad memory. Short of that it's a waste of lives and resources for no good purpose.