its not likely north korea will ever nuke anyone.
but the threat of doing so is easily enough to go to war over. and they arent just secretly building wmd's or the us/uk dont need to lie about this one, they are open about it and openly dangerous.
north korea has one of the largest armies in the world. granted they suck and we would peel them down in seconds, its just another ally for the bigger picture of russia and china. they likely dont give a stuff about the dozen war allies they have, its all more bodies to throw at the west lol.
china has like 20 disputed territories on all its borders.
an american hating, china loving, china bordering, nuke owning north korea makes a good friend, regardless of how useless he is.