The reason is "Apollo" system. To put it simply - it is too good. It is so good, that it basically eliminated all suspense from the combat sequences; there is no need for any strategy, tactics, inventiveness.
I must point out, that RFC could easily avoid such problem - simply by making the "Apollo" unreliable. And it would make perfect sense, actually. It is a revolutionary new system, designed during the time of severe military funding cuts, and then rushed into deployment. Historical experience generally tell us that such solutions led to... less than ideal success rate. Especially for the system that tend to break the basic physic laws in hard way (seriously, guys, "Apollo" system is based on combining somehow three different concepts of time - the dilated onboard time on the ship, the dilated onboard time on the missile, and some weird "absolute time" of FTL carrier wave. Not to mention, it breaks causality, i.e. it is working as time machine).
By making "Apollo" a capricious, unreliable systems, prone to malfunction, software and hardware bugs, RFC, frankly, could maintain the descent level of suspense and make us actually worry about the characters - because it would be always possible that they would NOT be able to just annihilate the enemy, and may be forced to fight it old-fashioned way. It wouldn't matter even if they still won the absolute majority of battles by Appolinating


Again, it is all my IMHO. But unless the reliability of "Apollo" system would be seriously compromised in the future (or retconned in the past, by adding, for example, some side battle, in which RMN was pounded due to system jinx) - I'm afraid, that one of the best parts of the series would be completely reduced to nothingness.