When performing a reply to message in forum I tend to like to be able to read the original post (as I cannot remember the entire original post).
Therefore I click on the radio button near the bottom of the Reply window to include (quote) the original post.
Next I enter a well written reply (a few minutes of my time)
Then, not wishing to clutter the forum with a regurgitation of the original post, I click the radio button to not quote the original post.
What happens here is "poof" goes my well crafted reply.
Kind of dissuades people from making high quality replies.