I personally don't think it (the reason most don't eat their own chickens) is deep or metaphysical or anything like that. This is BACKYARD chickens, and look at the recent poll Nifty did, most on this site have had chickens two years or less, and I would bet most peoples flocks are under 10 and live in a urban or suburban area.
The act of killing any animal (let alone one you know) doesn't come easy to anyone not raised to it, but the act of going to the grocery store is easy, chicken for the most part is inexpensive to buy at the grocery. We are all good at tuning out or distracting ourselves from unpleasent things we know are going on in the world (not just badly treated meat animals) just as long as it doesn't affect us directly, we have to in order to walk out our door in the morning with all the violence, and injustice (world wide) that we live with.
While I deplore the conditions most meat animals are in, on the grand scale of world wide evil that isn't even in the top 10. (predation on children physically, sexually, emotionally, unimaginable famine, war including attempts at genocide, human slavery, animal poaching to extinction, toxic waste in our air, water, and soil, nuclear and oil "accidents", deforestation of the worlds rain forests, etc......)