The way I had it explained to me was that serviceable MANPADs out there are currently fairly rare. They are a status symbol to own, but are mostly 1 shot only. Hence, if you fire it you are then without your status symbol, plus if you miss you become a bit of a laughing stock. This all leads to anyone who owns one to be happy with just owning it. Bragging rights preserved etc.
Also it's easier and cheaper to have a bash at a helo with an RPG.
Nice to hear that the Yanks are catching up with how UK FJ have been doing businees since the start. If it stops civi casualties and de-risks blue on blue I'm all for it.