Why does the ED based S530F, R-27s, IR missiles, etc. still use the older missile API?

[DSplayer]

Why do the older missiles like the S530F, R-27s, AIM-9 and other IR missiles, R-77, etc. still use the older weapon API compared to other missiles like the AIM-120s and AIM-7s? I know the AIM-54 specifically hasn't been ported to the new API/scheme system because the AIM-54 has features that isn't aren't really possible with the new API iirc but what prevents porting over other SARH missiles like the S530F (which was newly added) and the R-27 family over since the "aa_missile_semi_active" schema is already used by other SARH missiles? 

[falcon_120]

Resources, which mean free time of the team members in charge of the weapons systems. They'll come at some point.