Casual Interplanetary Travel-The joys of anti-gravity and gravity drive technology, you can reach a lot of destinations in days if not hours, easily. Civilian ships can accelerate up to 5-6Gs, with military warships able to accelerate up to 12Gs and do so as long as they have fuel for their fusion reactors. So long as the gravity drive doesn’t decouple (i.e. be unable to provide acceleration or deceleration at velocities over 50% to 70% of the speed of light), most ships use high acceleration torchship trajectories.
So far, nobody has done the whole “planet cracker done cheap” because (a) nobody thinks in terms of that kind of violence, (b) it’s hard and isn’t satisfying to rule a pile of rubble, and (c) in many ways, the wealth is from the living beings on the planet, not any material resources (many of which are easier to get from space).