I did not either for quite a while, then it dawned on me that there actually is a pretty good rationale for it. In this case too, it has nothing to do with firing the gun, but with safe manipulation.
In the second position (intermediary position with firing pin blocked but bolt movement allowed) one can unload a cartridge from the chamber WHILE KEEPING THE FIRING PIN LOCKED, or empty a magazine by cycling the cartridges in and out of the chamber (for those who do not want to open the bottom of the magazine or who have locked their magazine bottom to avoid inadvertent ammo dumping under recoil) WHILE KEEPING THE FIRING PIN LOCKED, which is clearly safer than doing so with a bolt ready to fire should the trigger be inadvertently touched during unloading manipulations.
Clever guy this Paul Mauser
I have actually modified some 2 position firing-pin-blocking safeties (which is easy to do) to allow opening the bolt while the firing pin is still blocked, jut to be able to unload the gun while keeping the safety on.
I agree with that concept on a PG rifle or with somebody who does not use a rifle as often as others.
On my DG rifles, I prefer two position safety. Safe and fire.
Gun safety is up to the person handling the firearm. During my military career that was drilled into me so many times and on such a consistent basis that it became second nature.
I carried that through to my hunting career. There is never a loaded rifle on my truck. I will never sling or shoulder a loaded rifle(on safe or not). When action is imminent and I chamber a round the rifle is always in both my hands whether the safety is engaged or not.
I see the point for the addition safety when emptying a rifle. With the controlled feeds I use, I push the bolt forward just as far as it needs to go to get the cartridge to come out the magazine and then back to eject.
Never ever had an issue with that but then I am very conscious of what I am doing when operating the bolt of a rifle.
Another thing that got drilled into me was how many rounds I have actually fired, as soon as the last one goes I instinctively go for the bullets that I carry on a wristband. I know at any given time how many bullets I have left in the rifle. If at all possible I always reload(top up) after each shot.
I have however seen on more than one occasion hunters not push the safety far enough forward with a three position safety and then obviously miss the opportunity to take a shot. This can also start screwing with your mind when needing to get into action under stress.
I am all for gun safety but personally prefer the good old two position variety.