For me these seem more organic just because they were the go-to agencies for so long (still ongoing for Holo). People have confidence that when Hololive announces a new generation every talent will be the best of the best and therefore they're more likely to sub with 0 information on the channel besides the presence of the little blue Dorito. Just anecdotal obviously, but I was subbed to all of Justice before they debuted and even though I don't actually like any of the talents enough to actively watch them I never went and unsubbed. There's no world, however, where I have enough confidence in V4Mirai to produce an entire gen good enough for me to preemptively subscribe to all of the talents.