It may have come about since we have seen so few VF-19s in service. What people should keep in mind is that the focus of each series is very limited. You're only seeing what occurs around the characters of the story. There's lots more stories and people out there so we never see beyond the scope of the story. If Zola could purchase a VF-19P, then that must mean something. I see the lack of VF-19s in service based on need. M7 never needed VF-19s for most of their voyage so why replace something that's not broken, and the VF-11s on-board M7 were upgraded to C-versions. And they haven't run into any major problems until they met the Varuata army. But this was only M7. It doesn't say anything for any of the other fleets out there. There could be a fleet out there that went for the VF-19 instead of upgrading to the VF-11C, or VF-14, or whatever. The truth is, we don't know because the story isn't focus on every fleet, just 1 or 2.