Why is Mew not in legends arceus?

Why is Mew not in legends arceus? Mew has never made an appearance in the Sinnoh region. Hence, it only makes sense that it would not make an appearance in the Hisui region as well since the two are in the same area. Every other Mythical Pokemon aside from Darkrai, Shaymin, Manaphy, and Phione are not and will not be present in Pokemon Legends: Arceus.

Mew has never made an appearance in the Sinnoh region. Hence, it only makes sense that it would not make an appearance in the Hisui region as well since the two are in the same area. Every other Mythical Pokemon aside from Darkrai, Shaymin, Manaphy, and Phione are not and will not be present in Pokemon Legends: Arceus.