I play the game in 3rd person for a number of reasons. None of which are about unfair advantage versus other players. In fact I haven't killed one person in the standalone, and in the mod I only killed in self-defence.
Since vision is our only sense (I find sound non-directional and filled with irrelevant ambient noises) I simply don't have a decent perspective of what is going on around me. I use 3rd person to give me more awareness.
In such a huge map, with such detail, things get a little clunky. I find moving in 3rd person means less getting caught on door frames etc.
I like the aesthetic of seeing my character wearing all the gear I worked so hard to scavenge.
My computer renders 3rd person better than first person (the same with Arma 3).
As far as realism goes, it's a game about ZOMBIES for God's sake! We're running around an island where there are more weapon modifications than there are can openers; houses contain more hospital grade medical equipment than utensil; and I can run for kilometres where a motorcycle helmet without either breaking my neck or overheating.
I'm sure all of that can be rationalised away through some fiction, so why not just pretend that a side effect of the zombie virus is a mutation that allows people to see around corners.
I promise not to force you to play in 3rd person, just don't make me play in 1st person.