There are over a billion YouTube accounts. Which single one do you assume I'm talking about? Lol. There are thousands, if not millions, that block comments and either hide their subscriber count or falsify it with software. Either way, it's usually done to make you channel look more popular than it really is. I would never block comments for any reason. There's always aholes that want to leave crap comments, but they are such a minority it doesn't matter. I guess if the majority of comments are bad or negative, an account owner might want to disable the comment option though.
WE all know exactly which one you are talking about. My fault for assuming you had more integrity then you are showing with your posts.