The noise aspect, Silence!

He's over there! Ninja:
I don't know about you but I don't have any grand intentions of sharing my meals with strangers in the event I'm using my pellet gun to obtain food. I think we can all pretty well agree that in such a scenario we are looking out for ourselves and loved ones. Sure, the thought of banding with others and reforming society one small group at the time is a nice notion and eventually it will have to occur, however, the primary objective is always going to be food, water, shelter for me and my own. Now, nothing says "HEY! I'M OVER HERE!" like a gun shot. This is exactly why there is a nationally recognized signal for distress involving them (3 gunshots 1 sec apart, same as whistle blasts). It may even be beneficial to be located this way in some scenarios, but I can't see that being the norm.

One thing that is so nice about air rifles is they tend to be much quieter than conventional firearms (excluding some pcp air guns). A typical 22lr will produce between 130 and 140 decibels when fired (I do not have the equipment to measure this, I am going off what others have measured, replicated, and shown on youtube and other such sites. If you would like some reference to how loud that is you can try this website, it tends to be pretty decent information.). Air rifles on the other hand can be very very quiet with some high velocity rifles in the 86-91 decibel range, if your slinging heavy lead the numbers can go down even further, on the flip side high velocity rifles with pba ammo can get up into the 120 decibel range (for more information on this, or specific air gun reviews, you can consult Paul Capello's Airgun Reporter). My point though is this, in order to get a 22lr into the same decibel range you would have to use subsonic ammo or a sound suppressor, OR BOTH! (do you really want to go through that much red tape? I know I don't). Theres nothing wrong with sub sonic ammo, but at that point what have you gained over the air rifle? Your velocity is the same or lower than the air rifle, your energy is very similar, and the cost for the subsonic 22lr is exponentially higher than lead pellets.

When it comes to keeping your position hidden while putting food on the table, the pellet rifle reigns supreme.

On a side note, I will give a personal example. I have fired, extensively, my Benjamin Trail NP in the middle of the city, while it was raining and you COULD NOT hear the shots. It really is amazing how quiet some of these rifles can get.