Speaking as someone who grew up in a shit hole filled with those kind of people it's because they're morons who think they're tough, at least the bikers aren't fighting for murderous psychopaths. I seriously believe that a percentage of the twats I knew at school will have likely gone and fought for ISIS because it's notably calmer around where I live now considering what it's usually like. Look on the bright side, at least we know where all the psychopaths are now
also in regards to going to Iraq, it's because of the law, nothings stopping them from killing people in a warzone because the soldiers and police are too busy fighting.
The same thing applies for the bikers, the government won't do anything if they're only fighting ISIS because ISIS is classed as a terrorist group and like with Turkey stopped the Kurds from crossing the border it wouldn't look very good if they were stopping people who wanted to go and fight a bunch of murderers.
