Do you consume the skin?
of an apple? a pear? a peach? or a big grape?
Fish and chicken on the other hand...unless it's fried, no.
I find the texture of peach skin unappetizing.
Some less common varieties of apples, pears, and grapes have bitter skin and taste better peeled.
I've heard that some people eat kiwis (the fruit, not the bird or person) with the skin on. It must feel like stubble on the way down.
Beyond issues of personal preference (not liking peach fuzz, for example), I think the deciding factor is organic vs. conventional agriculture.
If the fruit is organic, I'll usually eat the skin since that is where much of the fiber is located. It's also less hassle.
If the fruit is conventional, I'm more inclined to peel since the skin is where pesticide residues may be concentrated. If the fruit is waxed, peeling becomes a must.
For fruit - always.
Chicken - never.
Salmon - sometimes, depending on the preparation and my mood.
Fish (generally) - no.
Pork - only if it's deep fried and very crisp
Duck - never; not even Peking.