The chickens roost in the trees, even though they have a fine chicken house with clean bedding and so on. They feel safer up high. When Lucy hatched her first young brood, Ricky came down out of the trees at night to stay with the family. Some human beings don't do that much for their offspring. Chickens provide us with a significant protein in the form of eggs and meat.
Roosters are a part of that process.
To make sport of them in a fight to the death is unfair. That's a good question. My beautiful roosters, all in the image of the Kellog rooster, could have several destinies, but each of those with humane considerations. I do not exclude killing them but it must be done with knowledge. As our society strays further from its rural heritage we see more cruelty towards farm animals than before, usually through a blend of ignorance and lack of time and lack of space.