If the christian god is so "all powerful" Why is the devil still around?

In the bible it says he is the main enemy of god, if god was so powerful then why not just strike him down? He is the creator god in christianity, and can destroy him in a second but he chooses not to. Is he keeping the devil for a scare tactic? Scare people into following him and his religion? I have 0 belief in christianity(im an eclectic neo-pagan) but i do want to get my answer. IS the christian god honestly that hungry for followers?