Because some people love the story so much that they think about it in their spare time and wonder, "What's gonna happen next?" and sometimes we voice what we think might happen or how we invision it going down. It doesn't mean the author has to change it but sometimes there might be a little something in those request that will spark something in your mind and make you think... "Now maybe that was a good idea."
Oooh, I wholeheartedly agree. I've never actually "changed" a story before, because of what someone has said, but I have added parts or scenes in there that worked with the story, because someone wanted to see it or I thought it would improve my story.
(Oh, to quote a particular line above Jojo: "It doesn't mean the author has to change it" -- so does this mean you are still going to send men with pointy sticks my way about the ending of one particular story that I'm writing? Hmmm? I'm only kidding! Well, maybe... )
Smile and the world smiles with you ... frown and you're just giving yourself wrinkles.
I'm only kidding! Well, maybe... 
)
