Why does Resi 4 never get mentioned / referenced in the later games?

Whenever they do nostalgia stuff and callbacks, it's always about Raccoon city. It's always references to Resi 2 and 3.

Leon is traumatised because of Raccoon city. Why not Resi 4 as well? Why does he never mention it.

It's just weird to me that Resi 4 had such a huge cultural impact and was such a seminal game, and many people's favourites yet it's forgotten about in - universe