There is a game, actually a grandfather to all modern first-person games, named Wolfenstein 3D.
And its title screen explains very quickly what is wrong with 3rd person view considering realism.
Just look - do you see it?
See, title screen shows a moment that will never occur in the game itself (because game is in first-person view, of course): BJ Blazkowicz is aware of enemy soldier… while in-game, player has to move out from corner to see enemy and enemy gets alarmed instantly. Ability to peek around corners in 3rd person is very unrealistic and afaik, KCD has some stealth elements. So I’d rather not have any 3rd person view.