If you pay for your web site, feel free to do what like. With places like Github, things become a bit more complex. First of all, I assume you are not paying for those repositories. So I think it is decent to not randomly waste such a free offer. It also makes it more difficult to search for serious projects, if it is full of spam.

On the other side, in my experience, there is almost no code, which is so silly that it is useless. Quite the contrary, a lot of my best code pieces started with some sillines. It is sad, if code, which the creator made the effor to upload, is wasted, because of a poor license choices.