FOV: is there a technical reason it's capped?

[On2wheels]

I fired up TLD last night to try the new maps, it's been months since I played so I was excited to see all the new updates. Once it loaded I was instantly reminded of one of the main reasons why I stopped playing it; the narrow FOV.

I know many games are designed around a narrow FOV, and expanding it later in development can be difficult if it introduces model clipping or too much fisheye effect. I won't dig up the old debate on how much is too much because it's up to the user to decide, I'm more curious why the slider is capped and if there's reasons it's not letting us go more.

I'm aware of a steam forum thread with instructions of how to tweak it manually but it's unclear if it still works, and really, if it's possible to go more, why not just update the options menu?