This place is usually filled with depressing matters, I guess its EPs way to avoid having rep wars or something on here.
Actually I favor monoply's answer, thats pretty spot on
On EP, a lot of the people here have low self-esteem. So if you keep clicking the 'dislike' button it'll probably kill them! ...And I don't think that'll do well for advertisement revenue by losing all of those potential clicks. 0_o
It keeps things positive and discourages 'hating' but you can always give a thumbs down on YouTube.