It's less genuine caring and more just another excuse for tribalfagging. "NijiENs don't interact with fans" is pretty patently dumb, considering that this is the same branch in which multiple members spent a considerable amount of time hanging out with fans on VRChat. Luca would probably spend all day hanging out with fans if management let him. The girls also tend to quite frequently remember fans by name. Granted this is possible due to them having smaller chats than HoloENs, but the end result is that they're far more interactive with their fans than HoloEN, which has people like Gura who couldn't really interact much with her chat even if she wanted to. They're also very chatty with their fans on Twitter. If you are into vtubers for the appeal of getting noticed, you're far more likely to get that notice from a NijiEN liver.
I think it's also telling that most of this tribalfagging occurs after m/f collabs, even though f/f ones aren't exactly more prone to being "inclusive" to fans. The Rosemi-Elira-Enna-Millie offcollab featured them flirting quite blatantly with each other, way more so than any m/f collab.