The space borne planetary invasion force is a staple of many Sci-fi genres and most space invasions face the need to destroy some, or all, ground based infrastructure from orbit in order to take over a world. One of the things that often puzzles me is the depiction of lasers or particle beams for targeted ground attacks. These weapons would seem to tend to be dispersed or deflected by atmospheric gases and planetary magnetic fields.
that orbital dropped munitions are at least as accurate as modern smart bombs.
that you have access to "dialable damage" kinetic weapons for attacking ground side infrastructure.
that you want the planet you've gone to the trouble of invading largely intact, so no cobalt bombs or other long-term area-denial weapons.
that these weapons, while extremely useful for hammering planetary targets, are too slow moving for ship-to-ship combat and as such are not used as combat vessels' primary weapons.
that such weapons are not excessively large and can be mounted on/carried by warships without compromising their primary mission capability.
that planetary bombardment is rare in other circumstances but almost always necessary to support invasion forces.
For what practical reasons would weapon systems which are more suited to ship-to-ship combat be used in this planetary mass destruction role when they appear to suffer issues of accuracy and loss of power due to atmospheric effects and possibly cause excessive/secondary damage effects as a result of either heat bloom or, as in the case of nuclear or particle beam weapons, the nature of their operation?