Gamers who play first first person shooters do not grasp the simple concept that Stealth does not even exist in first person.
In order for stealth to exist in a game, it requires specific elements that only exist in third person. First person view completely strips all stealth elements out of a game for a number of reasons. People who argue the following points, simply do not understand how stealth actually works and only go by their first person gaming preference to argue these points. Walking up behind an enemy in a game and knocking them out in first person is not the same as doing it in third person.
First person view blocks up to 90% of the view that is needed in order for stealth to be possible.
First person view removes any and all distance judgement which is a requirement in stealth.
Stealth absolutely requires the player to know what is going on around them, first person removes this so you're no longer actually playing, you're now doing what's called guessing.
There is a reason why games like Splinter Cell, Metal Gear Solid, Assassin's Creed, Mortal Kombat, Devil May Cry, and Resident Evil are not in first person.
Removal of or not including 3rd person in a Thief game, turns it into just another run of the mill first person view game that destroys it.
You cannot play Stealth without the elements of Stealth being there to use, and first person removes all the elements that make stealth possible. And as I said above, people that argue against this with any type of justification simply does not understand how stealth works.