Why do you need to peel peaches to can them? I am going to be canning a bunch of peaches tonight, and I know that you have to peel them first (and I know how to do it easy), but I got to wondering, why do I have to do it?

I have always done it.  That is the way it was taught to me by my mother, but why?

The inside is the part that wants to rot, the out side is the protective coating (or so it seems).  Why do we need to remove it to can the peach?
My opinion- I haven't done rigorous testing: 

Canning softens the interior of the peach but when I have (in my laziness) left the skins on they stay tough and quite unpleasant tasting.

I doubt it has any effect on the longevity of the product but it would make it a little less pleasant and versatile.