North Korea 'fires missile from Pyongyang'

Getting something high is comparatively easy, getting something fast enough to orbit is a lot harder.

Ballistic missiles follow a ballistic trajectory, there's a high initial impulse and then gravity takes over. Generally, you want the most efficient ballistic trajectory because every kg you save in fuel is 1 more kg for the warhead.

IIRC, it's to do with getting high, and using gravity/momentum to reach targets further away, rather than flying straight to them. That's my very dumbed down understanding anyway.

https://en.wikipedia.org/wiki/Trajectory_of_a_projectile