No one plays RNG because it costs gil, is finicky to play with all the distance restrictions and despite those two annoyances, it only does decent not exceptional damage. Because no one plays the job, no one buys the ammo. Because no one buys the ammo, no one makes the ammo. Because no one makes the ammo, no one farms the mats.

I think, at this point, RNG is so stigmatized that even fixing the job to be the uber DD it was meant to be, will not change the situation. SE should just accept that fact and make ammo available from an NPC just like QD cards. No one crafts those and it hasn't ruined crafting.