Why? It has a lower Vf, and I believe the same footprint. It is more efficient than the 219B and has higher output, so it would be a prime candidate for an AAA unless there's something I'm missing. I prefer the tint of the 4000K 219B over almost everything else, but the efficiency and higher output would be nice in the AAA platform.
I don't know. Maybe it's the cost? or maybe it's the availability of the HCRI bin. Nichia C HCRI only became available on OCT 2016. A modder named V54 sells Lumintop tool with Nichia219c.
Okay, I thought you were saying there may be some technical reason why. Availability should get better, but availability of Nichia and Hi-CRI Cree have always been much lower than standard Cree's. I think with the high efficiency, and Hi-CRI of the new Nichia 219C that it will become more common than the 219A/B were.