Here is a bit of exploratory speculation.



Space (and air) superiority is a thing. Artificially disallowing it seems bizarre at best.



There are ways around this. Imagine for a moment you and up to three friends are going to take on a base. This base is either:



1) Covered by lots of point defense to shoot down rockets/missiles/bombs/ships. If you've ever seen the scene in Flash Gordon where Sky Rocket Ajax is on its way to the imperial palace, that is what I'm talking about. Lots of gun fire everywhere.



2) Covered by a planetary defense shield, so you have an explanation of why SRVs are required to get in besides "reasons". Perhaps you can have an SRV get in, shoot the generator then let your pals do the bombing run.



3) Lots of fighter cover. Either SLFs or regular ships.



It might be that the game engine just can't handle that level of stuff flying about, though.