I guess there is a difference between how accurate a rifle NEEDS to be, and how accurate we WANT it to be.
Even for big game like deer, which I routinely harvest within 100 yards, there is no NEED for my gun to shoot sub-moa. BUT, I admit that I WANT a rifle to shoot sub-moa, even under such circumstances. Why? Well, for one, it is a confidence builder. I know, you may ask "how much confidence do you need to shoot a deer at 100 yards?" Well, the answer to your question in part lies with my second reason: precision shooting. You see, I use a rifle as somewhat of a precise surgical tool. I know, that may seem funny, but consider how I hunt. There are times when I want to take a neck shot, or a spine shot. If you miss such a shot by an inch, then you could risk causing more pain to the animal. Granted, I now no longer take spine shots because it ruins to much meat, but I still take neck shots, especially on does, so that I purposely don't ruin too much meat. No, there is really nothing wrong with the typical lung shot, but I do tend to prefer the "cleaner" neck shot because, in part, my eyes and my hands are still skillful and sharp enough to allow me to take such shots.
In addition, there are other times where precision shooting is required on big game at shorter distances. Another such example is hog hunting. I used to (and sometimes still do) hunt these tenacious beasts with guns as powerful as a .375H&H. However, I have personally seen and witnessed many hunters shoot (and kill) big boars with the little .223. How? Well, they simply shoot the hogs right in their ear which leads to the brain. And let me tell you, they go down like lightning. Personally, I haven't used a .223 on hogs (at least not yet), but I have used shot a difficult shot with other cartrdiges such as the .270 Winchester, .30-06, 7mm Rem Mag, and others that I can't think about right now. And these shots were around 100 yards or so too, and you know that the target the size of a hogs ear hole is quite small. So, for such precision/surgical shooting, you need an accurate rifle.
I know that some people do not advocate head shots and neck shots. That's fine, that is if it's aimed towards unskilled shooters. However, for those shooters who are skilled enough, they are the best shots because not only do they generally ruin less meat, but they drop in their tracks and you don't have to try and find your animal over a long distance into thick cover.
Zachary