Is there a reason some lore pieces aren't voiced?

I noticed on several occasions that some lore pieces of important character like e.g. Maligaro's Manifesto in Act 7 - Chamber of Sins aren't voiced.

Why is that?
It really does break immersion when most lore pieces are voiced to then find some pieces which aren't.

So, for some reason, Acts 5-10 were thin on lore and none of it was voiced EXCEPT for the one single Love Letter at Vaal Ruins. I remember GGG promising an update that will add voices, but sadly, doesn't seem to be the case. Here's hoping POE 2 will add voices to Acts 5-10, but it seems super unlikely.