Because saying "X is worse than Y" is not useful unless you provide reasons as to why you believe that.
Imagine being someone reading your post. What are they to think? "Oh, this person says X is worse than Y -- I'll go ahead and take their word for it, despite no justification"? That's them buying into an appeal to your authority.
Now imagine if you'd actually provided reasoning. "Oh, this person says X is worse than Y because Z -- Z is a good point, therefore this is useful!" How different.
Providing baseless opinions is not useful, which is why you got downvoted; and incidentally, it's the exact same reason why you should "care to elaborate".