Someone please explain the existence of this platform to me.

With the MP5 phased out by MK18ish 5.56 SBR's in favor of better ballistics, why would someone convert their AR to 9mm?

From those I have seen, 9mm AR's are usually short barreled, probably around 8-10', so the switch wasn't a step-up over the 8.9" MP5 barrel.

The only viable reason I can see for this type of conversion, at the Dept. level, is perhaps its easier and cheaper to convert a stable of M4's or Colt Commandos to 9mm instead of purchasing MP5s. If this is the case though, why would they even switch to the 9mm from the 5.56 to begin with?

Is there any logical reason for this, besides simply because they could?