It's all about the player base. Currently a lot more people are playing packs on the FTB launcher than on the Curse client. And consequently, there are a lot more packs for them. The client will be, and in a lot of ways already is, the better system, so this is a way of moving people over to it. It's mostly targeted at people who already have packs on FTB, not at drawing new people in, or people who just have their packs on Curse.Understandable, but I highly doubt anyone is going to go out of their way to make a version for FTB launcher when curse is so much easier.