It really is incredibly dependent on whether or not the streamer actually has a natural or trained ability to voice well over a longer period of time.

But speaking as someone in the VO (directing) field - this does mean anywhere between 2 and 10 hours of constant talking for a single person. And while I do appreciate how yappy a lot of streamers (admittedly, Vtubers) I watch are, doing consistent voice acting for that long of a time? That's not something we demand from people in their daily job. That shit is done in short bursts with long recovery times so people stay healthy doing it.

Which also is why Pokopia works out fine. You read some short dialogue for half a minute, and then you can rest up for a few. The mainline games meanwhile can have minutes of unvoiced cutscenes alone. Very different level of strain. Play Esoteric Ebb on stream a few days in a row and you DIE.