So i have a half-baked theory about why they don't, or aren't going to implement a fov slider. In short, if they add it to PC only, console folks will get upset and their heads will explode, complaining about how the developers don't care for consoles.
On the other hand, if they add it there as well, then the consoles will blow up, since they are already pushed to the limits and increasing the fov will also eat away at the fps.

Came up with this genius explanation on my way to find Philippa Eilhart and bring her to ... blind justice? haha, get it?

But anyways, all joke aside, they really need to add in a fov slider, it just doesn't feel like a pc game without it and people are already complaining about headaches and such.