Probably because it's a cheap crappy way to get views. If you make a legitimate video response about a video, it will be accepted. But don't expect help getting your videos are responses to random videos as a cheap tactic.
Agree, you might get views if you leave a video but if it's unrelated content, you'll get a good handful of dislikes... People who come to your channel see that and it really puts a aesthetic tarnish on your "first impression".
Now, if you get dislikes for related content, that's just haters being haters... or your video must really be just that bad.