No, Far Cry 4 isn't missing that feature, you're just a pirate

Far Cry 4 gamers on PC who complain that the game has no field-of-view controls are outing themselves as playing pirated copies of the game.

This is per the game’s director, Alex Hutchinson, who noted that pirated copies lack the visual feature. It was applied to the game through a day-one patch.

Whoops.

Yes, legit copies of Far Cry 4 have an FOV slider. Here, for example, is what happens when you drive it all the way up and get on a fast vehicle (via r/pcmasterrace)

Developers have trolled pirates with game-crippling devices in the past. Most recently, The Sims 4 put an ever-growing pixelated blur on the screen of pirated copies. Other examples include the notorious immortal pink scorpion of Serious Sam: BFE, and Game Dev Tycoon, in which pirates have their virtual games virtually pirated until their studio goes out of business.