HK-47 said:
The Lovecraftian horrors have never appeared in non Persona SMT games to my knowledge.
Plus there is cooler stuff they need to put in first.
Nyarlathotep was in SMT2, if..., and Devil Survivor
Lovecraft stuff in SMT games, from the MegaTen Wiki:
* Byakhee (EP)
* Dagon (SMT1)
* Hastur (EP)
* Nodens (EP)
* Nyarlathotep (Persona 1, 2 IS/EP, SMT2, if..., Devil Survivor)
* Shoggoth (P2, doesn't specify which)
* Whateley (P2)
EDIT: And apparently Cthulhu was in SMT2. Never seen him mentioned before. And what the hell is that cock doing there?
As for the P2-only ones, they look a lot more like Soejima's work than Kaneko's, which might explain why they haven't been reused.