The precious thing about innocence is that it safely assumes things without any need to ascertain one way or another.
Preserving innocence is important, not because assuming is how one should go about things (that would be ignorance), but because once you feel the need to ascertain one way or another, it is no longer safe. It's less about protecting yourself from others than from your own need to know.
Because the loss of innocence is being too aware. Like walking a tightrope and being unable to look at anything but the distance below you. Because innocence is looking ahead and a steadiness in traversing - regardless of the risk, which is always there.
And how much easier is it to fall when it's all you see?