I think people who assume that orbital bombardment would be the norm underestimate the political implications. I am pretty sure it would be considered a war crime and space warfare under the geneva conventions or a smilar accord.
The norm? No. But the threat of inescapable death from orbit is terrifying, and could cow billions of people into submission. If the enemy has orbital superiority, or supremacy, they have your balls in a vice. Nowhere is safe, and unless you can somehow intercept thousands of rods or missiles screaming down at ten kilometers
a second AND shoot down vessels in orbit, you're doomed unless you do as they say. A few hundred satellites armed with rods or nukes could ensure obedience, and it's a lot easier to intercept something struggling against gravity to reach you than it is to shoot down something using gravity to gain speed. If the ground targets are huge cities, the carnage could be immense. If they're little habitation shelters on some barren, airless rock of a planet, a few direct hits could kill the whole colony.
As for political ramifications, they matter little if your fleet is strong enough to defeat anyone else's and threaten any planet. Earth (if united) will naturally have an enormous advantage over any colony for a long time because of its head start, seemingly infinite population, and control over vital resources. A lot of colonies would be entirely dependent on Earth for a very long time just to survive. All planets within any distance that's reachable anytime soon lack basic things like organic soil, air, building materials, and so on, so the threat of bombardment wouldn't even be necessary; the threat of blockade is enough.
All told, war is hell, and war in space is even worse because of the potential to cause or threaten incredible destruction at little to no risk to oneself. It should be avoided as much as possible, but since people and states seem to be completely psychologically incapable of leaving each other well enough alone, military power will be essential to avoid being totally at someone else's mercy.
Not if precision munitions were used. I mean, who says orbital bombardment has to involve mass devastation and firing all guns with reckless abandon?
Limited strikes are always an option. Guerrilla activity on the ground? Pinpoint and destroy with an armed satellite. Enemies of the state holed up in a building? Drop a meter-long rod on it from orbit. People hiding in an underground bunker? Drop a Massive Ordnance Penetrator on it. Or maybe you could even have human or robotic soldiers stationed in orbit who could be dropped planetside on short notice. Control of orbit and space gives people terrifying capabilities. It's even deadlier than air superiority. Again, this is horrible, but people cannot leave well enough alone, so they'll always look for new and exciting ways to kill each other.
